Programmed release oral solid pharmaceutical dosage form
This is a continuation of application Ser. No. 08/179,227, filed Jan. 10, 1994, now U.S. Pat. No. 5,445,828, which is a divisional of application Ser. No. 08/015,669, filed Feb. 9, 1993, now U.S. Pat. No. 5,310,558; which is a continuation of Ser. No. 07/724,930, filed Jul. 2, 1991, now abandoned. 
    
    
     The present invention relates to an oral solid pharmaceutical dosage form and, in particular, it relates to an orally administrable solid pharmaceutical dosage form from which the release of the drug begins after a programmed time interval from the administration. 
     Such dosage forms will be hereinafter indicated as programmed release dosage forms thus referring to an oral solid pharmaceutical dosage form which releases the active ingredient after a programmed time interval (no-release interval) from the administration, in contraposition to prompt release dosage forms which release the active ingredient practically completely at the moment of the administration and to controlled release dosage forms which slowly and gradually release the active ingredient starting from the moment of the administration. 
     A programmed release pharmaceutical dosage form is useful for the treatment of various pathologies. 
     It is known, in fact, that the treatment of many pathologies requires high hematic concentrations of drug in a restricted time and, preferably, also at an established time (Novel Drug Delivery and Its Therapeutic Application--Edited by L. F. Prescott &amp; W. S. Nimmo--John Wiley &amp; Sons--Chichester 1989). 
     Examples of such treatments are those directed to pathologies involving biological processes subjected to circadian rhythms [Clinical Pharmacokinetics, 7, 401, (1982)] such as the regulation of the blood pressure, the hormonal release and the chronobiology of asthma. Another example is the treatment of myocardial infarction and other cardiac diseases. 
     Further examples are the treatments involving rapidly metabolized drugs or drugs acting on receptors which are inactivated by a long lasting interaction with the drug (tolerances. 
     For such treatments a prompt release dosage form has the inconvenience to require several daily administrations while a controlled release dosage form fails to achieve a therapeutic concentration. Consequently, the programmed release of drugs such as for example antihypertensives, hormones, cardiotonics, antiasthmatics, antitussives allows to optimize the beneficial effects of the drugs by reducing their side-effects. 
     In addition, a suitable no-release interval can represent a mean to assure the site-specific release within particular regions of the gastro-intestinal tract, for example, within the colon. 
     This is particularly useful for the treatment of colon pathologies such as local infections, local spasms, tumors, ulcerous colitis and Chron&#39;s disease. 
     The colon, moreover, represents the best site for the release of certain systemically acting drugs. 
     In fact, it is known that the release of certain systemically acting drugs within the colon represents a valuable solution for the systemic absorption of drugs which are not orally administrable because susceptible to the action of the digestive enzymes (Science, 233, 1081-84, 1986). 
     Specific examples of drugs which are susceptible to the action of the digestive enzymes are peptides and proteins, such as insulin, gastrin, pentagastrin, calcitonin, glucagon, growth hormone, corticotropin, enkephalins, oxytocin, parathyroid hormone, vasopressin and the like. 
     Up to now only suppository pharmaceutical forms have been developed for the release of drugs within the colon. However, such pharmaceutical forms are not always able to assure an effective release within the colon [Int. J. Pharm., 25, 191-197, (1985)]. 
     The therapeutical importance of a programmed release orally administrable dosage form, for example in the above illustrated applications, prompted many Researchers in the pharmaceutical Industry as well as in the University to devote relevant efforts to achieve such a goal. 
     To the best of our knowledge, however, no programmed release orally administrable dosage form is yet available on the market. 
     European Patent Application No. 040590 (Aktiebolaget Hassle) describes an oral pharmaceutical form in which a core containing the active ingredient is coated by an anionic polymer, soluble at a pH higher than 5.5, and by a water-insoluble layer. 
     However, this phamaceutical form cannot assure the effective release within the colon since the release of the active ingredient, being pH dependent, can begin after only 1-2 hours from the administration. 
     International Patent Application No. WO 83/00435 (J. B. Tillot Ltd.) describes a solid oral form coated only by an anionic polymer which does not dissolve while passing through the upper gastro-intestinal tract. In order to assure the integrity of this solid oral form up to the colon, however, large amounts of the anionic polymer are necessary. 
     Moreover, also the release of this dosage form is pH dependent. In European Patent Application No. 366821 in the name of Istituto De Angeli S.p.A., a multilayered tablet for the release of a drug after a suitable time interval and especially in the colon is described. Such a pharmaceutical dosage form consists of a core and of an outer coating. 
     The coating consists of an inner layer of an anionic copolymer, containing a suitable plasticizer, of an intermediate layer of a gelling polymer and, finally, of an outer layer of a gastro-resistant polymer. 
     Such a tablet too has the inconvenient to be pH dependent. 
     Since the pH value of the gastro-intestinal tract is variable, also within physiological ranges (see for example Novel Drug Delivery and Its Therapeutic Application, above cited, Chapter 9, page 91-92) pH dependent pharmaceutical dosage forms do not always warrant an effective release of the drug at the programmed times and sites. Beside the above described pH dependent dosage forms, another approach studied for obtaining the release of a drug in the intestine is that of using a coating of a material susceptible to enzymatic degradation (see for example European Patent Application No. 343993--Agric. and Food Res.; International Patent Application No. WO 87/01588--Soc. Etud. Ile-de-France; U.S. Pat. No. 4,663,308--Medical College of Ohio). 
     With this approach too, the release of the drug depends on physiological factor which can vary from individuals to individuals. British Patent No. 1,346,609 in the name of Daiichi Seiyaku Company Limited and European Patent Application No. 274734 in the name of Pharmaidea S.r.1. describe multilayered tablets containing the active ingredient mixed with a superdisintegrant. 
     Each tablet is completely coated, except for a face, with an impermeable substance while the free face is coated with a layer of gelling and/or permeable material. 
     The water, which penetrates through the permeable layer, swells the superdisintegrant so splitting off the permeable layer and allowing the release of the drug. 
     It is clear to the man skilled in the art the very difficult industrial realization of such pharmaceutical dosage forms which require particular care in selectively coating all the surfaces of the tablet, except one, with an impermeable substance and then in coating the free face with a permeable material. 
     To the best of our knowledge, no industrial machinery is yet available for achieving such a selective surface coating. 
     A pharmaceutical dosage form constituted by spheres containing an inert core, for example a sugar core, coated with a drug and further coated with a disintegrant and, finally, with an outer coating of a water-insoluble and permeable material has been described in U.S. Pat. No. 4,871,549 in the name of Fujisawa Pharm. K.K. 
     The spheres, which have a diameter of about 1 mm, release the drug after a certain period which depends on the thickness of the outer coating, by means of the explosion of such coating due to the swelling of the disintegrant, which constitutes the intermediate layer. However, some drugs cannot be film coated onto the core making this pharmaceutical dosage form not always suitable. 
     Moreover, it is particularly difficult from a technological point of view to obtain a homogeneous thickness of the water-insoluble outer layer of the spheres because of their very small diameter. 
     In fact, the only practical realization of this dosage form under development, as far as we know, consists of a mixture of small spheres having different thickness of the water-insoluble outer layer so obtaining a controlled release. 
     An object of the present invention is that of providing an orally administrable solid pharmaceutical dosage form which releases the drug after a programmed time interval from the administration. 
     Another object of the present invention is that of providing an orally administrable solid pharmaceutical dosage form which releases the drug after a programmed time interval and which can be easily prepared in industrial scale by means of normally available industrial machinery and standard procedures. 
     Another object of the present invention is that of providing an orally administrable solid pharmaceutical dosage form which releases the drug after a programmed time interval that does not depend on the pH of the gastro-intestinal tract. 
     Still another object of the present invention is that of providing an orally administrable solid pharmaceutical dosage form which releases the drug after a programmed time interval that shows minimum variations among different individuals. 
     A further object of the present invention is that of providing an orally administrable solid pharmaceutical dosage form suitable for delivering a drug in the colon. 
     These and other objects which will be evident to the man skilled in the art are achieved by a pharmaceutical dosage form prepared by coating a normal orally administrable solid pharmaceutical preparation with a layer comprising a mixture of a hydrophobic material with a surfactant and optionally a water-soluble film forming material. 
     Therefore, object of the present invention is a programmed release oral solid pharmaceutical dosage form comprising an orally administrable core, containing the active ingredient, coated by a layer comprising a mixture of a hydrophobic material having a melting point between 50° C. and 90° C. and a surfactant having a HLB value between 10 and 16, the amount of the surfactant being from 5 to 20% by weight with respect to the hydrophobic material, and optionally a water-soluble film forming material in an amount of from 5 to 30% by weight with respect to the hydrophobic material. 
     For the sake of simplicity, we indicate hereinafter the layer comprising a mixture of a hydrophobic material with a surfactant and optionally a water-soluble film forming material, according to the invention, as &#34;the hydrophobic layer&#34;. 
     From the programmed release dosage form object of the invention the drug is released after a pre-established time interval which depends mainly on the thickness of the hydrophobic layer while it is independent of the pH value as well as of the motility of the gastro-intestinal tract. 
     At the end of this time interval, the drug is released with a kinetics which depends only on the kind of the pharmaceutical preparation constituting the core of the dosage form. 
     In other words, after the programmed time interval the drug is released rapidly if the core is a prompt release preparation or is released slowly if the core is a controlled release preparation. This second alternative is particularly useful as far as drugs for the specific treatment of the colon are concerned. 
     Thus, the core of the dosage form object of the present invention is any solid orally administrable pharmaceutical preparation and, in particular, prompt release or controlled release tablets and capsules. 
     The hydrophobic material in the hydrophobic layer is constituted by fats or other hydrophobic substances having a melting point between 50° C. and 90° C. 
     Examples of useful hydrophobic materials are esters of higher fatty acids with higher alcohols, higher alcohols, higher fatty acids, esters of glycerin with higher fatty acids, esters of higher fatty acids with polyethyleneglycol and mixtures of two or more thereof. 
     Specific examples are carnauba wax, beeswax, cetyl alcohol, stearyl alcohol, hard paraffin, microcrystalline wax or petroleum wax, stearic acid, myristic acid, hydrogenated castor oil, tallow and mixtures of two or more thereof. 
     Preferably, the surfactant in the hydrophobic layer is selected among non-ionic surfactants or mixtures thereof. 
     Suitable surfactants are esters of polyethoxylated fatty acids with sorbitan and ethoxylated fatty alcohols. 
     The amount of surfactant is between 5 and 20% by weight with respect to the hydrophobic material and preferably about 10%. 
     Further examples of substances useful as the hydrophobic layer, according to the invention, are the substances known as &#34;Gelucire&#34; (trademark of Gattefosse Company), that is mixtures of mono-, di- and tri-glycerides and di-esters of polyethylene glycol. 
     The water soluble film forming material in the hydrophobic layer is an optional because its main function is that of ensuring the adhesion of the hydrophobic layer on the core. 
     When used, it is used in the minimum amount useful fop ensuring the adhesion and this amount is between 5 and 30% by weight with respect to the hydrophobic material, preferably about 15-20%. 
     Exclusively for practical reasons, it is preferred to use the water-soluble film forming material. 
     Examples of water-soluble film forming materials are hydroxyalkyl-celluloses, polymethacrylic acid esters and polyvinylpyrrolidone. 
     It is worth noting that all the components of the hydrophobic layer of the invention are well-known and pharmaceutically acceptable materials, most of which being already approved by the Pharmacopoeias of several Countries. This represents a relevant advantage of our dosage form. 
     In this connection, we wish to underline that, even if these materials are well-known in pharmaceutical technology, they have only been used in different ratios and for different aims with respect to the present invention. 
     For example, it is known the use of hydrophobic materials, such as waxes, also in admixture with a surfactant or with a film-forming material for the preparation of controlled release dosage forms (Sustained and Controlled Release Drug Delivery System--Edited by Joseph R. Robinson--Marcel Dekker, Inc.--New York and Basel; J. C. Colbert--Controlled Action Drug Forms--Noyes Data Corporation 1974), for the preparation of enteric coating (European Patent Application No. 19546--The Procter and Gamble Co.) or for taste-masking purposes (U.S. Pat. No. 4,341,582--Sankyo Co. Ltd.). 
     The pharmaceutical dosage forms object of the invention are suitable for the administration of many drugs in the treatment of various pathologies. 
     In practice, all the drugs which have physico-chemical characteristics suitable for the preparation of a solid pharmaceutical preparation, like tablets and capsules, can be used. 
     Examples of drugs which, in the treatment of the above reported pathologies, receive a therapeutical advantage from the instant dosage forms are: antihypertensive, antiasthmatic, mucolytic, antitussive, antiallergic, anti-inflammatory, antirheumatic, antiarthritic, capdiotonic, antispasmodic, hypnotic, anxiolytic, antineoplastic, analgesic and antibacterial drugs, proteins and hormones and also drugs useful in veterinary field. 
     Specific examples are: hydralazine, minoxidil, prazosin, enalapril, broxaterol (USAN and the USP Dictionary of Drug Names, 1991, United States Pharmacopoeial Convention Inc.), albuterol, dextromethorphan, cromolyn, acetylcysteine, dropropizine, ibuprofen, diclofenac, naproxen, aspirin, ketorolac, mesalamine, indomethacin, sulfasalazine, diltiazem, ibopamine, isosorbide mono- and di-nitrate, nitroglycerin, propranolol, oxprenolol, alprenolol, cimetropium bromide, insulin, gastrins, pentagastrin, calcitonin, glucagon, somatotropin, ACTH, endorphins, oxytocin, parathypoid hormone, vasopressin, cortisone, corticosterone, alprazolam, triazolam, oxazepam and zolpidem, optionally as salts with pharmaceutically acceptable acids or bases and, when the drugs are chiral, also in an optically active form. 
     If not otherwise specified, for a comprehensive reference to the above listed drugs see The Merck Index, eleventh edition, 1989, published by Merck &amp; Co., Inc. 
     The preparation of the dosage form of the invention is carried out according to usual procedures and by means of standard machineries. In practice, a dispersion or solution in water op in organic solvent of the hydrophobic material, the surfactant and, optionally, the water-soluble film forming material is film coated on a core containing the active ingredient. 
     The coating is carried out according to conventional film coating methods. 
     The core is a prompt release or controlled release pharmaceutical composition consisting of the active ingredient in admixture with suitable excipients. 
     If necessary, the core can be protected by a water-soluble film before coating with the hydrophobic layer. 
     By means of the pharmaceutical dosage form object of the invention, the no-release interval may be programmed by selecting the appropriate thickness of the hydrophobic layer and, the thickness being equal, by selecting the kind of hydrophobic material. 
     Obviously, the thickness of the hydrophobic layer is determined by its weight. 
     Inside the indicated melting point range, lower melting hydrophobic materials result in a longer no-release interval. 
     On the contrary, inside the indicated weight range, the amount of surfactant in the hydrophobic layer does not significantly influence the no-release interval. 
     In the same way, the site of the release may be programmed too. 
     For the practical realization, the dosage form consisting of the core and the hydrophobic layer is preferably used when the goal is the release of the active ingredient after a pre-established time interval from the administration, independently of the site in which the release occurs. 
     In this case, depending on the posology of the drug to be administered, it may be useful to associate a prompt release dosage form to the programmed release dosage form of the invention, so obtaining two doses of active ingredient at different times with one administration. 
     This realization may be useful also in order to obtain the contemporaneous administration of two different active ingredients, so acting at different times, with one administration. 
     These results may be achieved by contemporaneously administering a prompt release dosage form and a programmed release dosage form of the invention, for example, in a capsule containing both of them. 
     In alternative, the same result may be achieved by further coating a programmed release dosage form of the invention with an outer prompt release layer containing the same or another active ingredient. 
     When the goal is the release of a drug in a specific target site, e.g. the colon, the selection of the appropriate hydrophobic layer will take into account the time necessary for the transit through the stomach as well as the time necessary for the transit through the small intestine. 
     However, the time necessary for the transit through the stomach can vary within a large range, from some minutes to several hours, depending mainly on the presence or not of food. 
     This fact is not relevant when the goal is the release of a drug after a pre-established time interval, while it becomes important when the goal is the release of a drug in the colon. 
     Therefore, in this second case, the dosage form should be administered between meals or after a light meal. 
     In alternative, by coating the dosage form of the invention with an enteric coating, that is a gastro-resistant coating, the selection of the appropriate hydrophobic layer will take into account the time necessary for the transit through the small intestine only, the no-release interval of this enteric coated dosage form being independent of the time necessary for the transit through the stomach. 
     The enteric film coating is carried out with conventional methods by using known enteric polymers in an organic solvent or in aqueous solvent. 
     Suitable polymers for the enteric coating are, for example, cellulose acetate phthalate, methacrylic acid-methacrylic acid ester copolymers, hydroxypropylmethylcellulose phthalate, polyvinyl acetate phthalate, hydroxyethylcellulose phthalate, cellulose acetate tetraphthalate. 
     To the above indicated polymers, suitable plasticizers such as, for example, polyethylene glycol, dibutylphthalate, diethylphthalate, triacetin, castor oil, citrates may be optionally added. 
     Furthermore, talc or other lubricants and optionally coloring agents for pharmaceutical use may be added to the enteric film in order to improve the final characteristics of the product. 
     Thus practical embodiments of the pharmaceutical dosage form according to the invention are: 
     a tablet constituted by a prompt release core, containing the active ingredient, coated by the hydrophobic layer p1 a tablet constituted by a controlled release core, containing the active ingredient, coated by the hydrophobic layer 
     a tablet constituted by a prompt release core, containing the active ingredient, coated by the hydrophobic layer and further coated by an outer prompt release layer containing the same or another active ingredient 
     a capsule, containing the active ingredient, coated by the hydrophobic layer 
     a capsule, containing the active ingredient, coated by the hydrophobic layer and by an outer enteric coating 
     a capsule containing a prompt release tablet and a programmed release tablet 
     a tablet constituted by a prompt release core, containing the active ingredient, coated by the hydrophobic layer and by an outer enteric coating 
     a tablet constituted by a controlled release core, containing the active ingredient, coated by the hydrophobic layer and by an outer enteric coating. 
     It is not yet clear the mechanism by which the dosage form of the invention affords the release of the drug after a pre-established time interval from the administration. 
     Since this result does not depend on the pH and on the specific gastro-intestinal tract (as shown in example 2), it appears that it does not depend on chemical or biochemical reactions. 
     Tentatively, the observed effect may be explained by a physical interaction of the dosage form with the body fluids resulting in a slow and uniform dispersion of the hydrophobic layer until the intact core gets in contact with the body fluids and the drug is released. 
     In view of the fact that the mechanism by which the release is delayed is not yet known, it may be difficult to precisely forecast the duration of such interval a priori. 
     However, the desired no-release interval results to be a direct function of the thickness (i.e. weight) of the hydrophobic layer, as shown in Example 19, and to a lesser extent it is a function of the other parameters, in particular the melting point of the hydrophobic material. 
     A very good correlation exists between a simple and readily available in vitro release test and the observed in vivo release. 
     The in vitro test, which is herewith provided in details in example 1, shows how the in vitro no-release interval corresponds to the average no-release interval in human beings (see examples 2 and 3) with a very good correlation. 
     Accordingly, the examples reported in the specification give to the man of the art a sufficient guidance for the selection of the parameters affording the desired no-release interval and the simple in vitro test confirm the expected result or gives guidance for modifying the selected parameters inside the range provided by the invention. 
     The pharmaceutical dosage form object of the invention shows several advantages with respect to the prior art. 
     First of all, the programmed release of the drug makes the pharmaceutical dosage form object of the invention suitable for various drugs which are used in pathologies subjected to biological rhythms thus optimizing the beneficial effects and decreasing their side-effects. 
     The programmed release of the drug within particular regions of the gastro-intestinal tract, especially within the colon, makes the pharmaceutical dosage form object of the invention suitable for several drugs for which a different release-site causes a detrimental or less useful therapeutical effect. 
     It is possible to prepare such pharmaceutical dosage forms in a simple and economic way by using conventional methods and machineries. 
     The no-release interval does not depend on the pH of the gastro-intestinal tract or on other physiological parameters. This advantage, which is relevant with respect to known compositions having the same purpose, makes the dosage form of the invention suitable also, for example, for patients having a not physiologic gastro-intestinal pH, such as patients suffering from achlorhydria or taking H 2  -antagonists or antiacids. 
     With the aim to better illustrate the present invention the following examples are now given. 
     The present invention is not intended to be limited in scope by the following examples since each is intended merely as an illustration of the invention. 
     Modifications of the invention in addition to those shown and described herein become apparent to the man skilled in the art from the foregoing description and from the examples. 
     Such modifications are intended to fall within the scope of the invention. 
    
    
     EXAMPLE 1 
     General procedure 
     Preparative methods 
     The preparation of the cores, on which the hydrophobic layer is affixed, was carried out by using usual excipients and conventional preparative techniques. 
     By film coating according to known methods (coating pan or fluidized bed), the thus obtained cores were coated with a previously prepared dispersion containing the hydrophobic material, the surfactant and, optionally, the water-soluble film forming material. 
     The preparation of this dispersion was carried out by melting the hydrophobic material with the surfactant at a temperature between 80° and 90° C., then, by adding subsequent small portions of boiling water under suitable stirring and, finally, by cooling up to room temperature. 
     When used, an aqueous solution of the water-soluble film forming material, prepared by adding the water-soluble film forming material to boiling water under stirring and by cooling up to room temperature, was added to the dispersion. The resultant suspension was filtered (180 mesh), then film coated on the cores and dried under air flow. 
     Before film coating, the cores may be protected by a water-soluble film. 
     The final pharmaceutical dosage forms can be further coated with an outer layer of enteric coating. 
     The preparation of the enteric coating can be, for example, carried out by diluting a commercially available aqueous dispersion and by affixing it on the dosage form of the invention by usual film coating techniques (coating pan or fluidized bed). 
     If not otherwise specified, the excipients used for the preparation of the pharmaceutical dosage forms described in the following examples are: 
     Polyvinylpyrrolidone: the material commercialized by BASF Company with the trademark &#34;Kollidon K 30&#34; was used. 
     Crospovidone: crosslinked polyvinylpyrrolidone commercialized by BASF Company with the trademark &#34;Kollidon CL&#34; was used. 
     Colloidal silica: the material commercialized by Degussa Company with the trademark &#34;Aerosil 200&#34; was used. 
     Surfactant: polysorbate 80 commercialized by ICI Americas Company with the trademark &#34;Tween 80&#34; was used. (HLB 15±1) 
     Enteric polymer: methacrylic acid-methacrylic acid ester copolymer commercialized by Ro Pharm. Company with the trademark &#34;Eudragit L30D&#34; was used. 
     PEG 6000: polyethylene glycol 6000 (Merck Index, XI Ed., No. 7545, page 1204) 
     Hydroxypropylmethylcellulose: hydroxypropylmethylcellulose having viscosity=5 cP was used for the water-soluble film. hydroxypropylmethylcellulose having viscosity=15 cP was used for the hydrophobic layer. 
     In vitro release evaluation 
     The in vitro release of the active ingredient was determined by dissolution test (Apparatus 2 and 3, USP XXII, page 1578-1583). 
     The in vitro evaluation was carried out in Apparatus 2 at 100 r.p.m. The obtained data were confirmed by carrying out the same test at 50 r.p.m., in water, in simulated enteric medium, in pH 1.2 buffer, in pH 5.5 buffer, in pH 6.8 buffer and in Apparatus 3 without disks. 
     The obtained data confirmed that the no-release interval is independent of the pH. 
     In vivo release evaluation 
     The in vivo release of the active ingredient was determined by gamma scintigraphy [S. S. Davis, &#34;Evaluation of the gastro-intestinal transit of pharmaceutical dosage form using the techniques of gamma scintigraphy&#34;, S.T.P. Pharma, 2, 1015-1022, (1986)]. 
     For the evaluation of the time of the release as well as of the site of the release, samarium oxide was used as a component of the core. The pharmaceutical dosage forms were irradiated and the resultant labelled dosage forms were administered to healthy volunteers. 
     The gamma radiation was recorded by gamma camera. 
     Correlation between in vivo and in vitro data 
     The comparison between the in vivo and the in vitro release data shows a linear correlation. 
     In particular the in vitro no-release interval determined by the in vitro test carried out in a 3.3% sodium chloride aqueous solution gives substantially the same values as the observed in vivo no-release interval, while the in vitro no-release interval determined by a test carried out in water is half that observed in vivo. 
     EXAMPLE 2 
     Preparation of labelled tablets for the in vivo and in vitro release evaluation 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
E110 dye              3.0 mg                                              
samarium oxide (enriched in .sup.152 Sm)                                  
                      2.0 mg                                              
lactose               77.5 mg                                             
corn starch           13.5 mg                                             
polyvinylpyrrolidone  3.0 mg                                              
magnesium stearate    1.0 mg                                              
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.75 mg                                              
PEG 6000             0.08 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         32.3 mg                                              
beeswax              13.8 mg                                              
surfactant            4.6 mg                                              
hydroxypropylmethylcellulose                                              
                      9.2 mg                                              
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using a 3.3% sodium chloride aqueous solution (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and spectrophotometrically analyzed (482 nm) to detect the presence and the amount of the dye (E110) released by the core. 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
180          0                                                            
190          0                                                            
200          0                                                            
210          0                                                            
220          0                                                            
230          0                                                            
240          0                                                            
310          5.06                                                         
330          59.76                                                        
360          102.93                                                       
______________________________________                                    
 
    
     The dissolution test was carried out also in water only (500 ml). The release of the dye was observed at halved time intervals. 
     In vivo release evaluation 
     The in vivo release evaluation was carried out by gamma scintigraphy according to what described in example 1. 
     The tablets were administered to seven healthy volunteers after a light meal. 
     The following data were obtained. 
     
         ______________________________________                                    
volunteer      tablet disintegration (min)                                
______________________________________                                    
1              300                                                        
2              299                                                        
3              376                                                        
4              331                                                        
5              393                                                        
6              315                                                        
7              314                                                        
mean value     332.6                                                      
standard error mean                                                       
               14.1                                                       
______________________________________                                    
 
    
     In each volunteer the proximal colon was the release-site. 
     The in vivo release evaluation was carried out also by administering the same tablets to six different healthy volunteers after a heavy meal. 
     The following data were obtained. 
     
         ______________________________________                                    
volunteer      tablet disintegration (min)                                
______________________________________                                    
1              287                                                        
2              417                                                        
3              304                                                        
4              380                                                        
5              304                                                        
6              379                                                        
mean value     345.2                                                      
standard error mean                                                       
               21.8                                                       
______________________________________                                    
 
    
     The obtained data show that there is a good correlation between in vivo and in vitro release and that, with particular reference to the mean values, the food has substantially no influence upon the release-time. 
     Moreover, the standard error mean shows how the no-release interval has a minimum variation among different individuals. 
     These in vivo data further confirm the in vitro data concerning the independence of the no-release interval with respect to the pH of the gastro-intestinal tract. 
     EXAMPLE 3 
     Preparation of labelled tablets for the in vivo and in vitro release evaluation 
     The cores were prepared in a similar way to that described in example 2. 
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.57 mg                                              
PEG 6000             0.06 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         24.6 mg                                              
beeswax              10.6 mg                                              
surfactant            3.5 mg                                              
hydroxypropylmethylcellulose                                              
                      7.1 mg                                              
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using a 3.3% sodium chloride aqueous solution (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and spectrophotometrically analyzed (482 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 90          0                                                            
105          0                                                            
120          0                                                            
135          0                                                            
150          0                                                            
165          0                                                            
180          13.87                                                        
195          59.6                                                         
210          99.2                                                         
______________________________________                                    
 
    
     The dissolution test was carried out also in water only (500 ml). The release of the dye was observed at halved time intervals. 
     In vivo release evaluation 
     The in vivo release evaluation was carried out by gamma scintigraphy according to what described in example 1. 
     The tablets were administered to six healthy volunteers after a light meal. 
     The following data were obtained: 
     
         ______________________________________                                    
volunteer      tablet disintegration (min)                                
______________________________________                                    
1              206                                                        
2              189                                                        
3              188                                                        
4              189                                                        
5              225                                                        
6              225                                                        
mean value     203.7                                                      
standard error mean                                                       
               7.3                                                        
______________________________________                                    
 
    
     The obtained data show that there is a good correlation between in vivo and in vitro release. 
     EXAMPLE 4 
     Preparation of labelled enteric coating tablets for the in vivo evaluation of the release-site 
     The cores were prepared in a similar way to that described in example 2. 
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.75 mg                                              
PEG 6000             0.08 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax           30.0 mg                                            
beeswax                13.0 mg                                            
surfactant              4.3 mg                                            
hydroxypropylmethylcellulose                                              
                        8.6 mg                                            
A further enteric coating constituted by:                                 
enteric polymer         8.8 mg                                            
triacetin               0.8 mg                                            
______________________________________                                    
 
    
     was affixed. 
     In vivo evaluation of the release-site 
     The in vivo evaluation of the release-site was carried out by gamma scintigraphy according to what described in example 1. 
     The tablets were administered to six healthy volunteers after a light meal. 
     In each volunteer the colon was the release-site. 
     EXAMPLE 5 
     Preparation of tablets containing Ibopamine hydrochloride as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Ibopamine hydrochloride                                                   
                   55.95 mg                                               
polyvinylpyrrolidone                                                      
                   1.48 mg                                                
crospovidone       45.83 mg                                               
colloidal silica   0.42 mg                                                
stearic acid       0.42 mg                                                
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.20 mg                                              
PEG 6000             0.02 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         56.29 mg                                             
surfactant            5.63 mg                                             
hydroxypropylmethylcellulose                                              
                     11.26 mg                                             
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (900 ml) at 37° C. 
     At specific time intervals, a specimen (10 ml) was withdrawn and spectrophotometrically analyzed (220 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
 30          0                                                            
 60          0                                                            
 90          0                                                            
120          0                                                            
150          8.92                                                         
180          88.30                                                        
210          97.13                                                        
______________________________________                                    
 
    
     EXAMPLE 6 
     Preparation of tablets containing Ibopamine hydrochloride as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Ibopamine hydrochloride                                                   
                   42.00 mg                                               
polyvinylpyrrolidone                                                      
                   1.65 mg                                                
microcrystalline cellulose                                                
                   6.55 mg                                                
colloidal silica   0.40 mg                                                
stearic acid       1.80 mg                                                
lactose            33.70 mg                                               
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     2.67 mg                                              
PEG 6000             0.30 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        29.33 mg                                              
surfactant          2.93 mg                                               
hydroxypropylmethylcellulose                                              
                    5.87 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (900 ml) at 37° C. 
     At specific time intervals, a Specimen (10 ml) was withdrawn and spectrophotometrically analyzed (220 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           35.11                                                        
120          101.43                                                       
______________________________________                                    
 
    
     EXAMPLE 7 
     Preparation of tablets containing Broxaterol hydrochloride as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Broxaterol hydrochloride                                                  
                   0.569 mg                                               
polyvinylpyrrolidone                                                      
                   3.000 mg                                               
lactose            39.531 mg                                              
starch             56.000 mg                                              
magnesium stearate 1.000 mg                                               
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.90 mg                                              
PEG 6000             0.10 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        15.24 mg                                              
beeswax             6.53 mg                                               
surfactant          2.18 mg                                               
hydroxypropylmethylcellulose                                              
                    4.35 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent phosphate buffer/acetonitrile: UV detector at 216 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           0                                                            
120          60                                                           
150          98                                                           
______________________________________                                    
 
    
     EXAMPLE 8 
     Preparation of tablets containing Broxaterol hydrochloride as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Broxaterol hydrochloride                                                  
                   0.569 mg                                               
polyvinylpyrrolidone                                                      
                   3.000 mg                                               
microcrystalline cellulose                                                
                   95.531 mg                                              
magnesium stearate 1.000 mg                                               
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.49 mg                                              
PEG 6000             0.06 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        18.98 mg                                              
beeswax             8.13 mg                                               
surfactant          2.70 mg                                               
hydroxypropylmethylcellulose                                              
                    5.42 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent phosphate buffer/acetonitrile; UV detector at 216 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           0                                                            
120          47.3                                                         
150          77                                                           
180          100                                                          
______________________________________                                    
 
    
     EXAMPLE 9 
     Preparation of tablets containing Broxaterol hydrochloride as active ingredient 
     The cores were prepared in a similar way to that described in example 10. 
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.90 mg                                              
PEG 6000             0.10 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         38.47 mg                                             
beeswax              16.47 mg                                             
surfactant            5.47 mg                                             
hydroxypropylmethylcellulose                                              
                     10.98 mg                                             
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent phosphate buffer/acetonitrile: UV detector at 216 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
 30          0                                                            
 60          0                                                            
 90          0                                                            
120          0                                                            
150          0                                                            
180          0                                                            
210          0                                                            
240          0                                                            
270          33                                                           
300          67                                                           
330          102                                                          
______________________________________                                    
 
    
     EXAMPLE 10 
     Preparation of tablets containing Broxaterol hydrochloride as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Broxaterol hydrochloride                                                  
                       0.569 mg                                           
polyvinylpyrrolidone   3.000 mg                                           
lactose                77.431 mg                                          
starch                 18.000 mg                                          
magnesium stearate     1 mg                                               
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     7.41 mg                                              
PEG 6000             0.82 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        22.16 mg                                              
beeswax             9.50 mg                                               
surfactant          3.17 mg                                               
hydroxypropylmethylcellulose                                              
                    6.33 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7μm; eluent phosphate buffer/acetonitrile: UV detector at 216 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           0                                                            
120          70                                                           
150          102                                                          
______________________________________                                    
 
    
     EXAMPLE 11 
     Preparation of tablets containing Broxaterol hydrochloride as active ingredient 
     The cores were prepared in a similar way to that described in example 10. 
     The thus obtained cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        18.96 mg                                              
beeswax             8.13 mg                                               
surfactant          2.71 mg                                               
hydroxypropylmethylcellulose                                              
                    5.42 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent phosphate buffer/acetonitrile; UV detector at 216 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           7                                                            
120          78                                                           
150          100                                                          
______________________________________                                    
 
    
     EXAMPLE 12 
     Preparation of tablets containing Diclofenac sodium as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Diclofenac sodium   50.0 mg                                               
microcrystalline cellulose                                                
                    10.0 mg                                               
polyvinylpyrrolidone                                                      
                     3.0 mg                                               
lactose             25.0 mg                                               
corn starch         74.5 mg                                               
magnesium stearate   1.5 mg                                               
colloidal silica     6.0 mg                                               
sodium carboxymethylstarch                                                
                    20.0 mg                                               
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     3.6 mg                                               
PEG 6000             0.4 mg                                               
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         62.0 mg                                              
beeswax              26.5 mg                                              
surfactant            8.8 mg                                              
hydroxypropylmethylcellulose                                              
                     17.7 mg                                              
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (600 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and spectrophotometrically analyzed (276 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
270          0                                                            
300          12                                                           
330          87.5                                                         
360          99.2                                                         
______________________________________                                    
 
    
     EXAMPLE 13 
     Preparation of tablets containing Naproxen as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Naproxen          250 mg                                                  
polyvinylpyrrolidone                                                      
                  15 mg                                                   
corn starch       44 mg                                                   
magnesium stearate                                                        
                   5 mg                                                   
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     6.0 mg                                               
PEG 6000             0.7 mg                                               
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax        104.8 mg                                              
beeswax             44.8 mg                                               
surfactant          14.9 mg                                               
hydroxypropylmethylcellulose                                              
                    29.9 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using phosphate buffer (900 ml) at 37° C. At specific time intervals, a specimen was withdrawn and spectrophotometrically analyzed (330 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
360          0                                                            
390          16.9                                                         
420          73.7                                                         
450          104.3                                                        
______________________________________                                    
 
    
     EXAMPLE 14 
     Preparation of tablets containing Albuterol sulfate as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Albuterol sulfate 2.4 mg                                                  
lactose           77.5 mg                                                 
polyvinylpyrrolidone                                                      
                  3.0 mg                                                  
corn starch       16.1 mg                                                 
magnesium stearate                                                        
                  1.0 mg                                                  
______________________________________                                    
 
    
     The thus obtained cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         32.3 mg                                              
beeswax              13.8 mg                                              
surfactant            4.6 mg                                              
hydroxypropylmethylcellulose                                              
                      9.2 mg                                              
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent phosphate buffer/acetonitrile; UV detector at 276 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
180          0                                                            
190          18.6                                                         
200          50.8                                                         
210          71.4                                                         
220          92                                                           
230          101.2                                                        
______________________________________                                    
 
    
     EXAMPLE 15 
     Preparation of tablets containing Triazolam as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Triazolam           0.125 mg                                              
lactose             72.000 mg                                             
microcrystalline cellulose                                                
                    18.000 mg                                             
colloidal silica    0.300 mg                                              
dioctyl sodium sulfosuccinate                                             
                    0.850 mg                                              
sodium benzoate     0.150 mg                                              
corn starch         4.750 mg                                              
magnesium stearate  1.000 mg                                              
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     0.90 mg                                              
PEG 6000             0.09 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         25.0 mg                                              
beeswax              10.7 mg                                              
surfactant            3.6 mg                                              
hydroxypropylmethylcellulose                                              
                      7.2 mg                                              
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out by using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and analyzed by reversed-phase HPLC chromatography (RP 8 column, 7 μm; eluent water/acetonitrile; UV detector at 222 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 90          0                                                            
105          0                                                            
120          52.8                                                         
135          98.7                                                         
150          99.8                                                         
______________________________________                                    
 
    
     EXAMPLE 16 
     Preparation of tablets with controlled-release core containing Mesalamine as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Mesalamine       300.0 mg                                                 
ethylcellulose   76.4 mg                                                  
crospovidone     18.3 mg                                                  
magnesium stearate                                                        
                  6.2 mg                                                  
talc             10.4 mg                                                  
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     23.4 mg                                              
PEG 6000              2.4 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         140 mg                                               
beeswax              60 mg                                                
surfactant           20 mg                                                
hydroxypropylmethylcellulose                                              
                     40 mg                                                
______________________________________                                    
 
    
     A further enteric coating constituted by: 
     
         ______________________________________                                    
enteric polymer 47.0 mg                                                   
triacetin        1.3 mg                                                   
______________________________________                                    
 
    
     was affixed. 
     EXAMPLE 17 
     Preparation of tablets with controlled-release core containing Cimetropium bromide as active ingredient 
     The cores were prepared by conventional compression methods, each having the following composition: 
     
         ______________________________________                                    
Cimetropium bromide                                                       
                  50 mg                                                   
lactose           125 mg                                                  
starch            73 mg                                                   
magnesium stearate                                                        
                   2 mg                                                   
______________________________________                                    
 
    
     The thus obtained cores were coated with a protecting water-soluble film constituted by: 
     
         ______________________________________                                    
hydroxypropylmethylcellulose                                              
                     1.20 mg                                              
PEG 6000             0.12 mg                                              
______________________________________                                    
 
    
     Then, the protected cores were coated with a hydrophobic layer (prepared and applied as described in example 1) constituted by: 
     
         ______________________________________                                    
carnauba wax         67.0 mg                                              
beeswax              29.0 mg                                              
surfactant            9.6 mg                                              
hydroxypropylmethylcellulose                                              
                     19.0 mg                                              
______________________________________                                    
 
    
     A further enteric coating constituted by: 
     
         ______________________________________                                    
enteric polymer 17.0 mg                                                   
triacetin        0.5 mg                                                   
______________________________________                                    
 
    
     was affixed. 
     EXAMPLE 18 
     Preparation of soft gelatin capsules for the in vitro release evaluation 
     Each capsule contained: 
     
         ______________________________________                                    
E110 dye            6 mg                                                  
polyethyleneglycol 600                                                    
                   194 mg                                                 
______________________________________                                    
 
    
     The capsules were film coated by fluidization dip coating at a temperature below 50° C. using an aqueous dispersion of the following mixture: 
     
         ______________________________________                                    
beeswax             23.37 mg                                              
cetostearyl alcohol 5.85 mg                                               
surfactant          2.93 mg                                               
hydroxypropylmethylcellulose                                              
                    5.85 mg                                               
______________________________________                                    
 
    
     In vitro release evaluation 
     The in vitro release evaluation was carried out by dissolution test according to what described in example 1. 
     The test was carried out using water (500 ml) at 37° C. 
     At specific time intervals, a specimen was withdrawn and spectrophotometrically analyzed (482 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
time (min)   percentage of release                                        
______________________________________                                    
 0           0                                                            
30           0                                                            
60           0                                                            
90           0                                                            
120          0                                                            
150          78                                                           
180          102                                                          
______________________________________                                    
 
    
     EXAMPLE 19 
     Evaluation of the correlation between the thickness of the hydrophobic layer and the no-release interval 
     The in vitro release of the protected cores, that is without the hydrophobic layer, prepared as described in example 2, and with different increasing thickness of the hydrophobic layer, prepared and applied as described in example 1, was evaluated by dissolution test according to what described in example 1. 
     The hydrophobic layer was constituted by a mixture of carnauba wax, beeswax, surfactant and hydroxypropylmethylcellulose in the same weight ratios described in example 2. 
     The increase of the thickness of the hydrophobic layer was expressed as increase of the tablet diameter and as the corresponding increase of the tablet weight. 
     The dissolution test was carried out by using water (500 ml) at 37° C. 
     The beginning of the release was detected spectrophotometrically (482 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
diameter (mm)                                                             
          weight increase (%)                                             
                        no-release interval (min)                         
______________________________________                                    
5.50       0             0                                                
6.10      28             75                                               
6.50      48            135                                               
6.75      60            155                                               
7.00      73            180                                               
______________________________________                                    
 
    
     The same dissolution test was carried out by using the protected cores, that is without the hydrophobic layer, prepared as described in example 5, and with different increasing thickness of the hydrophobic layer, prepared and applied as described in example 1. 
     The hydrophobic layer was constituted by a mixture of carnauba wax, surfactant and hydroxypropylmethylcellulose in the same weight ratios described in example 5. 
     The beginning of the release was detected spectrophotometrically (220 nm). 
     The following data were obtained: 
     
         ______________________________________                                    
diameter (mm)                                                             
          weight increase (%)                                             
                        no-release interval (min)                         
______________________________________                                    
7.2        0             0                                                
7.3       11            15                                                
7.4       20            30                                                
7.7       40            90                                                
8.0       69            140                                               
______________________________________                                    
 
    
     The obtained data show that there is a linear correlation between the increase of the thickness of the hydrophobic layer and the increase of the no-release interval and that this correlation does not depend on the cores.