in the process of the invention , the preferred coacervation medium includes cyclohexane alone or in admixture with hexane . cyclohexane when saturated with chlorpheniramine maleate at 80 ° c . contains 148 . 8 micrograms of chlorpheniramine maleate per milliliter of cyclohexane . analytical testing has shown that there is no degradation of chlorpheniramine maleate in the cyclohexane so that recycling of the saturated cyclohexane is possible . preferably the chlorpheniramine maleate saturation of the cyclohexane is accomplished before the encapsulation process begins . the chlorpheniramine maleate to be encapsulated can be added to the pretreated cyclohexane alone or in conjunction with another pharmaceutical material , such as pseudoephedrine hydrochloride , with which it is commonly administered in a combined dosage form . preferably a mixture of the chlorpheniramine maleate and the other pharmaceutical material are granulated to form a drug combination having defined proportions of each ingredient for a suitable dosage form . for example , for a children &# 39 ; s dosage form the proportions can be 7 . 5 milligrams of pseudoephedrine hydrochloride and 0 . 5 milligrams of chlorpheniramine maleate . accordingly the drug ratio in the granular material and in the encapsulated granules would be 7 . 5 to 0 . 5 . the ethylcellulose suitable for use as the encapsulating polymer can be any of the commercial types customarily used for encapsulating purposes . a typical ethylcellulose has a 45 to 50 per cent ethoxyl content and a 95 - 110 cps viscosity . the amount of ethylcellulose employed can vary but for taste masking purposes , the ethylcellulose should comprise about 25 % to 35 % by weight of the coated granules . the ethylcellulose used in the following examples was ethylcellulose , nf manufactured by dow chemical company having a 49 . 4 per cent ethoxyl content and a 103 . 6 cps viscosity . the polyethylene suitable for use as the phase inducer can have a molecular weight of between 5 , 000 and 10 , 000 and can be any of the commercial types customarily used for encapsulating purposes . the amount of polyethylene employed depends somewhat on the type employed but the amount should usually provide a ratio to the ethylcellulose of about 4 : 1 to about 8 : 1 parts by weight of ethylcellulose per part by weight of polyethylene . the brand of polyethylene used in the following examples was epolene c - 10 , manufactured by eastman kodak company , viscosity at 150 ° c . of 8175 cps within the range of 7000 - 11000 cps and a softening point of 101 . 6 ° c . within the range of 95 °- 110 ° c . the process of the invention is now described below with reference to the specific examples . this example illustrates the use of the process of the invention to provide taste masked encapsulated granules of chlorpheniramine maleate and pseudoephedrine hydrochloride for incorporation into children &# 39 ; s tablets . the granules containing the raw drug were prepared by first preparing a mixture containing 33 . 4 - 36 . 9 % by weight of pseudoephedrine hydrochloride , 2 . 23 - 2 . 46 % by weight of chlorpheniramine maleate and the remainder being microcrystalline cellulose . because of the required low combination dosage level of the drugs the inert carrier was used to achieve acceptable dose level uniformity . the granulation was accomplished in this instance in a top spray fluid bed unit . the granules had a typical particle size range as shown below . ______________________________________us std . sieve # % retained______________________________________ 14 -- 30 -- 40 1 . 1 60 3 . 4 100 31 . 8 140 36 . 6thru 140 -- 200 18 . 3 270 6 . 3 pan 2 . 5 100 . 0 % ______________________________________ the granules may be prepared by other granulation techniques known to the art such as wet granulation . see for example u . s . pat . nos . 5 , 084 , 278 and 3 , 872 , 227 . the proportions of ingredients used in this example were as follows : ______________________________________cyclohexane 1000 gramspolyethylene c - 10 5 gramsethylcellulose nf 30 gramsgranules 90 gramschlorpheniramine maleate , usp 192 milligrams______________________________________ into a two liter glass beaker equipped with a 4 inch turbine and a switch blade baffle were placed the 1000 grams of cyclohexane together with 192 milligrams of chlorpheniramine maleate . the batch was heated to 80 ° c . with 250 rpm agitation using a heating mantle and an aluminum foil cover . the mixture was cooled to 35 ° c . the remaining ingredients were then added and the mixture was heated to 80 ° c . with 250 rpm agitation and use of the aluminum cover . once the temperature of the mixture reached 80 ° c ., the heat source was removed and the mixture was allowed to cool slowly to 35 ° c . with 300 rpm agitation . at 35 ° c . the contents of the beaker were decanted into a buchner filter with no washing and tray dried overnight . the microcapsules were sieved and a typical analysis is shown below in the second column of the table . in another experiment , the ingredient amount and operating conditions were the same as in example 1 except that the granule content was 60 grams and the ethylcellulose content was 20 grams providing a phase ratio of 3 : 1 but an ethylcellulose concentration of 2 %. the sieve analysis is shown in the third column of the table below . in a further experiment the ingredient amount and operating conditions were the same as in example 1 except that the granule content was 120 grams and the ethylcellulose content was 40 grams providing a phase ratio of 3 : 1 but an ethylcellulose concentration of 4 %. the sieve analysis is shown in the fourth column of the table below . ______________________________________particle size analysis % retained______________________________________us std . mesh 40 28 . 8 23 . 8 14 . 3 60 17 . 9 26 . 5 26 . 1 100 35 . 0 37 . 0 40 . 1 170 15 . 6 10 . 6 16 . 4 200 1 . 8 1 . 1 2 . 1 270 0 . 8 0 . 6 0 . 8 pan 0 . 1 0 . 4 0 . 2 100 . 0 % 100 . 0 % 100 . 0 % ______________________________________ the product of example 1 had an acceptable taste masking of the bitter taste of the pharmaceutical ingredients and had a good mouth feel . the product was of an appropriate particle size and met an acceptable release for in vitro requirements . process variables for the pseudoephedrine hydrochloride - chlorpheniramine maleate combination for taste masking purposes are a phase ratio of 2 : 1 through 4 : 1 parts by weight of granules per part by weight of ethylcellulose , a 2 % through 4 % concentration of ethylcellulose in cyclohexane , and a 0 . 4 through 0 . 65 % concentration of polyethylene in cyclohexane . operation variables include sufficient agitation to keep the microcapsules suspended in the coacervation medium during and after their formation and a temperature range including a maximum temperature of about 80 ° c . and a minimum temperature of about 30 °- 35 ° c . chlorpheniramine maleate should be heated with the cyclohexane as a first step to saturate the cyclohexane and the other ingredients can be added following standard microencapsulating procedure at a temperature sufficiently high to dissolve the ethylcellulose and the polyethylene . optimum values for the process variables are a phase ratio of 3 : 1 , a 3 % concentration of ethylcellulose in cyclohexane , a 0 . 5 % concentration of polyethylene in cyclohexane , and a total solids concentration of 12 . 5 % in cyclohexane to provide 25 % by weight ethylcellulose coated granules . with respect to recycling the coacervation medium , cyclohexane containing dissolved chlorpheniramine maleate was tested for possible degradation of chlorpheniramine maleate in this solvent . after five cycles of heating to 80 ° c . and cooling to 35 ° c ., no evidence of drug degradation was determined .
an improvement in the process of coacervation of chlorpheniramine maleate is provided whereby a predetermined amount of chlorpheniramine maleate charged to the process is maintained in the microcapsules by pre - saturating the coacervation medium with chlorpheniramine maleate .