the present invention relates to an osmotic delivery system for controlled delivery of a beneficial agent . fig1 - 4 illustrate two examples of osmotic delivery devices 10 according to the present invention . the osmotic drug delivery device 10 , as illustrated in fig1 includes a movable valve 28 , a first chamber 22 containing a beneficial agent , a separating member 20 , and a second chamber 24 containing an osmotic engine or agent , all of which are enclosed within an elongated substantially cylindrical enclosure or capsule 12 . the capsule 12 has a first end 14 and an open end 16 . the first end 14 of the capsule 12 has one or more orifices or ports 18 for delivering a beneficial agent contained within a first chamber 22 of the osmotic delivery device 10 to an external environment . in most configurations , one delivery port 18 will suffice . however , two or more delivery ports 18 may be present without departing from the present invention . the valve 28 occludes the delivery orifice 18 when the valve is in a closed position , preventing the beneficial agent in the first chamber 22 from leaving the delivery device 10 as well as preventing the incursion of foreign materials into the device . the dimensions of the valve 28 in terms of both diameter and length are selected such that the valve will not exit the delivery device 10 through the delivery orifice 18 . the separating member 20 also separates the first chamber 22 containing the beneficial agent from the second chamber 24 containing the osmotic agent . the separating member 20 and valve 28 are substantially cylindrical members which are configured to fit within the capsule 12 and are slidably movable along a longitudinal direction within the capsule . the separating member and valve 20 , 28 preferably are formed of a resilient material which is impermeable to the compositions within the capsule 12 , and at least a portion of the separating member 20 and the valve 28 forms a seal with the inner surface of said capsule 12 . in addition , the movable separating member and valve 20 , 28 may be flexible members such as pistons , partitions , pads , flat sheets , spheroids , or rigid metal alloys , and may be made of any number of inert materials . furthermore , the osmotic device 10 may function without the piston 20 , having simply an interface between the osmotic agent and the beneficial agent . a semipermeable membrane 30 couples with the capsule 12 at the open end 16 and encloses the second chamber 24 containing the osmotic agent . the osmotic agent may be , for example , a nonvolatile water soluble osmagent , an osmopolymer which swells on contact with water , or a mixture of the two . the elongated capsule 12 is formed of a material which is sufficiently rigid to withstand expansion of the osmotic agent contained within a second chamber 24 of the delivery device 10 without changing size or shape . the elongated capsule 12 is preferably substantially impermeable to fluids in the environment as well as to ingredients contained within the osmotic delivery device 10 such that the migration of such materials into or out of the device through the impermeable material of the capsule is so low as to have substantially no adverse impact on the function of the osmotic delivery device . as shown in fig1 and 2 , the osmotic delivery device 10 of one embodiment of the present invention includes a semipermeable membrane 30 , which is coupled with the open end 16 of the capsule 12 . in operation , after placing the osmotic agent within the second chamber 24 of the capsule , the semipermeable membrane 30 allows liquid to pass from an environment of use into the capsule 12 to cause the osmotic agent to swell . however , the material forming the semipermeable membrane 30 is largely impermeable to the materials within the capsule 12 and to other ingredients within the environment of use . the swelling osmotic agent exerts a pressure on the separating member or piston 20 and forces said separating member to move a distance d in a direction of the arrow a . the separating member 20 applies a force to the beneficial agent in the first chamber 22 , the beneficial agent transfers the force to the valve 28 . accordingly , this force causes the valve 28 to move a distance c from the close position to an open position . a clearance 34 between the valve 28 and the first end 14 decreases by the distance c . in the open position , the valve 28 allows the beneficial agent to pass through the delivery orifice 18 to the external environment of use . the osmotic agent in conjunction with the separating member 20 drive the beneficial agent from the first chamber 22 and insures a flow of beneficial agent out of the delivery orifice 18 . the valve 28 is retained within the delivery device 10 at the closed first end 14 of the capsule 12 and , as described above , the valve 28 has dimensions such that it will not leave the delivery device 10 through the delivery orifice 18 . in a preferred embodiment , the capsule 12 has a vent 32 at the first end 14 , allowing fluid to escape from the clearance 34 between the valve 28 and the capsule 12 when the valve 28 moves toward the first end 14 . depending on the application , the clearance 34 between the valve 28 and the capsule 12 may be filled with a bio - compatible liquid or gas . the configuration of the osmotic delivery system and the material of the semipermeable membrane 30 control the delivery rate of a beneficial agent from the osmotic delivery system . in assembling the osmotic delivery device 10 according to the embodiment of the present invention shown in fig1 and 2 , the capsule 12 is prepared by forming at least one vent 32 at the first end 14 of the capsule . the vent 32 may be formed by mechanical drilling , laser drilling , molding , or any other known method . the delivery port 18 is an orifice formed by conventional techniques which are known in the art . included among these methods are mechanical drilling , laser drilling , and molding . the dimensions of the delivery port 18 in terms of both diameter and length will vary with the type of beneficial agent , the rate at which the beneficial agent is to be delivered , and the environment into which it is to be delivered . the considerations involved in determining the optimum dimensions of the delivery port 18 for any particular capsule 12 or beneficial agent and the selection of the appropriate dimensions will be readily apparent to those skilled in the art . once the capsule 12 of fig1 and 2 has been prepared with the vent 32 and at least one delivery port 18 , having a number , shape , and size to achieve a desired delivery rate of the beneficial agent , the valve 28 is inserted into the capsule 12 through the open end 16 . according to one embodiment of the present invention , the beneficial agent contained in the first chamber 22 of the capsule 12 is a flowable composition such as a liquid , suspension , or slurry , and is typically poured into the first chamber 22 of the capsule after the valve 28 has been inserted . the separating member 20 is inserted into the capsule 12 through the open end 16 and is positioned adjacent the beneficial agent . once the osmotic agent pellet ( s ) or tablet ( s ) have been formed , they are placed inside the pre - formed capsule in the second chamber 24 adjacent the separating member 20 . then the semipermeable membrane 30 , according to one embodiment of the present invention , is placed into or over the open end 16 of the capsule 12 to close off and seal the open end of the osmotic delivery system . an alternative embodiment of the invention illustrated in fig3 - 4 includes a cap 36 having a hollow interior and a substantially constant thickness cylindrical side wall 42 and an end wall 44 . the cap 36 forms the first end 50 of the capsule 12 . in a preferred embodiment , the cap 36 affixes to the body of the capsule 12 by a snap fitting mechanism 38 , such as a barbed stake . the cap 36 preferably has a vent 48 in the end wall 44 which after assembly allows the valve 28 to move in a direction towards the end wall 14 . in a different embodiment , the cap 36 can be pivotally rotated about a hinge in a direction of the arrow b , as depicted in fig4 . the first chamber 22 of the osmotic delivery device 40 has at least one opening 46 which communicates with the environment of use . as shown in fig3 the opening 46 is formed in the body of the capsule 12 and is positioned adjacent the contacting surfaces of the cap . alternatively , the opening 46 can be formed in the cap 36 and positioned adjacent the contacting surfaces of the body of the capsule 12 . the semipermeable membrane 30 couples with the capsule 12 at the opened second end 52 . in assembling the osmotic delivery device 10 according to the embodiment of the present invention shown in fig3 and 4 , the cap 36 is prepared by forming at least one vent 48 at the end wall 44 . the vent 48 may be formed by mechanical drilling , laser drilling , molding , or any other known method . the capsule 12 is prepared having an opened first end 50 and an opened second end 52 . the delivery port 46 is an orifice positioned at the edge of the cap 36 adjacent the capsule 12 , or the delivery port 46 is positioned at the edge of the capsule 12 adjacent the cap 36 . the delivery port 18 is formed by conventional techniques which are known in the art . included among these methods are laser drilling , mechanical drilling , grooving the edge of the capsule or cap , and molding . the separating member 20 is inserted into the capsule 12 through the first or second end 50 , 52 . once the osmotic agent pellet ( s ) or tablet ( s ) have been formed , they are placed inside the capsule 12 in the second chamber 24 , adjacent the separating member 20 . the semipermeable membrane 30 is placed into or over the second end 52 to close off and seal that end . beneficial agent is added into the first chamber 22 of the capsule 12 through the first end 50 , and the valve 28 is inserted adjacent the beneficial agent in a closed position . as discussed , the valve 28 in a closed position prevents the beneficial agent from leaving the delivery device 10 and prevents incursion of foreign materials into the device . then the cap 36 is placed at the first end 50 of the capsule to close off and seal that open end of the osmotic delivery system 10 . the cap 36 may be secured to the capsule 12 by press fitting , snap fitting , threading , adhesive , welding , staking , or the like . in general , materials suitable for use in the movable separating member 20 and the valve 28 are elastomeric materials including non - reactive polymers , as well as elastomers in general , such as polyurethanes and polyamides , chlorinated rubbers , styrene - butadiene rubbers , and chloroprene rubbers . the polymers include acrylonitrile polymers such as acrylonitrile - butadiene - styrene terpolymer , and the like ; halogenated polymers such as polytetraflouroethylene , polychlorotrifluoroethylene , copolymer tetrafluoroethylene and hexafluoropropylene ; polyimide ; polysulfone ; polycarbonate ; polyethylene ; polypropylene ; polyvinylchloride - acrylic copolymer ; polycarbonate - acrylonitrile - butadiene - styrene ; polystyrene ; and the like . semipermeable compositions suitable for the semipermeable membrane 30 are well known in the art , examples of which are disclosed in u . s . pat . no . 4 , 874 , 388 , the entire disclosure of which is incorporated herein by reference . such possible semipermeable materials from which the membrane 30 can be made include , but are not limited to , for example , hytrel polyester elastomers ( dupont ), cellulose esters , cellulose ethers , and cellulose ester - ethers , water flux enhanced ethylene - vinyl acetate copolymers , semipermeable membranes made by blending a rigid polymer with water - soluble low molecular weight compounds , and other semipermeable materials well known in the art . the above cellulosic polymers have a degree of substitution , d . s ., on the anhydroglucose unit , from greater than 0 up to 3 inclusive . by “ degree of substitution ” or “ d . s .” is meant the average number of hydroxyl groups originally present on the anhydroglucose unit comprising the cellulose polymer that are replaced by a substituting group . representative materials include , but are not limited to , one selected from the group consisting of cellulose acylate , cellulose diacylate , cellulose triacylate , cellulose acetate , cellulose diacetate , cellulose triacetate , mono -, di -, and tricellulose alkanylates , mono -, di -, and tricellulose aroylates , and the like . exemplary cellulosic polymers include cellulose acetate having a d . s . up to 1 and an acetyl content up to 21 %; cellulose acetate having a d . s . of 1 to 2 and an acetyl content of 21 % to 35 %; cellulose acetate having a d . s . of 2 to 3 and an acetyl content of 35 % to 44 . 8 %, and the like . more specific cellulosic polymers include cellulose propionate having a d . s . of 1 . 8 and a propionyl content of 39 . 2 % to 45 % and a hydroxyl content of 2 . 8 % to 5 . 4 %; cellulose acetate butyrate having a d . s . of 1 . 8 and an acetyl content of 13 % to 15 % and a butyryl content of 34 % to 39 %; cellulose acetate butyrate having an acetyl content of 2 % to 29 %, a butyryl content of 17 % to 53 %, and a hydroxyl content of 0 . 5 % to 4 . 7 %; cellulose acetate butyrate having a d . s . of 1 . 8 , an acetyl content of 4 % average weight percent , and a butyryl content of 51 %; cellulose triacylates having a d . s . of 2 . 9 to 3 such as cellulose trivalerate , cellulose trilaurate , cellulose tripalmitate , cellulose trisuccinate , and cellulose trioctanoate ; cellulose diacylates having a d . s . of 2 . 2 to 2 . 6 such as cellulose disuccinate , cellulose dipalmitate , cellulose dioctanoate , cellulose dipentate ; coesters of cellulose such as cellulose acetate butyrate and cellulose , cellulose acetate propionate , and the like . other materials for the membrane 30 are polyurethane , polyetherblockamide ( pebax , commercially available from elf atochem , inc . ), and injection - moldable thermoplastic polymers with some hydrophilicity such as ethylene vinyl alcohol ( eva ). in general , the membrane 30 is made from semipermeable materials having a water uptake ranging from 1 % to 80 % but preferably less than 50 %. the composition of the semipermeable membrane 30 is permeable to the passage of external liquids such as water and biological liquids , and it is substantially impermeable to the passage of beneficial agents , osmopolymers , osmagents , and the like . materials which may be used for the capsule 12 and the cap 36 must be sufficiently strong to ensure that the capsule will not leak , crack , break , or distort under stresses to which it is subjected during implantation or under stresses due to the pressures generated during operation . the capsule 12 may be formed of chemically inert and biocompatible , natural or synthetic materials which are known in the art . the capsule material is preferably a nonbioerodible material which remains in the patient after use , such as titanium or a titanium alloy , and is largely impermeable to materials within and outside the capsule . however , the material of the capsule 12 may alternatively be a bioerodible material which bioerodes in the environment after dispensing of the beneficial agent . generally , preferred materials for the capsule 12 are those acceptable for animal and human implants . in general , typical materials of construction suitable for the capsule 12 according to the present invention include non - reactive polymers or biocompatible metals or alloys . metallic materials useful for the capsule 12 include stainless steel , titanium , platinum , tantalum , gold , and their alloys , as well as gold - plated ferrous alloys , platinum - plated ferrous alloys , cobalt - chromium alloys and titanium nitride coated stainless steel . the capsule 12 may be formed from any of the wall - forming materials disclosed above by the use of a mold , with the materials applied either over the mold or inside the mold , depending on the mold configuration . any of the wide variety of techniques known in the pharmaceutical industry may be used to form the capsule 12 . the osmotic agent is a liquid - attracting agent used to drive the flow of the beneficial agent . the osmotic agent may be an osmagent , an osmopolymer , or a mixture of the two . species which fall within the category of osmagent , i . e ., the non - volatile species which are soluble in water and create the osmotic gradient driving the osmotic inflow of water , vary widely . examples are well known in the art and include magnesium sulfate , magnesium chloride , potassium sulfate , sodium chloride , sodium sulfate , lithium sulfate , sodium phosphate , potassium phosphate , d - mannitol , sorbitol , inositol , urea , magnesium succinate , tartaric acid , raffinose , and various monosaccharides , oligosaccharides and polysaccharides such as sucrose , glucose , lactose , fructose , and dextran , as well as mixtures of any of these various species . species which fall within the category of osmopolymer are hydrophilic polymers that swell upon contact with water , and these vary widely as well . osmopolymers may be of plant or animal origin , or synthetic , and examples of osmopolymers are well known in the art . examples include : poly ( hydroxyalkyl methacrylates ) with molecular weight of 30 , 000 to 5 , 000 , 000 , poly ( vinylpyrrolidone ) with molecular weight of 10 , 000 to 360 , 000 , anionic and cationic hydrogels , polyelectrolyte complexes , poly ( vinyl alcohol ) having low acetate residual , optionally cross linked with glyoxal , formaldehyde , or glutaraldehyde and having a degree of polymerization of 200 to 30 , 000 , a mixture of methyl cellulose , cross linked agar and carboxymethylcellulose , a mixture of hydroxypropl methycellulose and sodium carboxymethylcellulose , polymers of n - vinyllactams , polyoxyethylene - polyoxypropylene gels , polyoxybutylene - polyethylene block copolymer gels , carob gum , polyacrylic gels , polyester gels , polyuria gels , polyether gels , polyamide gels , polypeptide gels , polyamino acid gels , polycellulosic gels , carbopol acidic carboxy polymers having molecular weights of 250 , 000 to 4 , 000 , 000 , cyanamer polyacrylamides , cross linked indene - maleic anhydride polymers , good - rite polyacrylic acids having molecular weights of 80 , 000 to 200 , 000 , polyox polyethylene oxide polymers having molecular weights of 100 , 000 to 5 , 000 , 000 , starch graft copolymers , and aqua - keeps acrylate polymer polysaccharides . the osmotic agent may be a solid osmotic tablet or a fluid osmotic agent . the osmotic tablet may be formed in many different conceivable shapes , textures , densities , and consistencies and still be within the confines of the present invention . the osmotic agent may be manufactured by a variety of techniques , many of which are known in the art . in one such technique , the osmotically active agent is prepared as solid or semi - solid formulation and pressed into pellets or tablets whose dimensions correspond to slightly less than the internal dimensions of the respective chambers which they will occupy in the capsule interior . depending on the nature of the materials used , the agent and other solid ingredients which may be included may be processed prior to the formation of the pellets by such procedures as ballmilling , calendaring , stirring , or rollmilling to achieve a fine particle size and hence fairly uniform mixtures of each . the present invention applies to the administration of beneficial agents in general , which include any physiologically or pharmacologically active substance . drug agents which may be delivered by the present invention include drugs which act on the peripheral nerves , adrenergic receptors , cholinergic receptors , the skeletal muscles , the cardiovascular system , smooth muscles , the blood circulatory system , synoptic sites , neuroeffector junctional sites , endocrine and hormone systems , the immunological system , the reproductive system , the skeletal system , autacoid systems , the alimentary and excretory systems , the histamine system and the central nervous system . suitable agents may be selected from , for example , proteins , enzymes , hormones , polynucleotides , nucleoproteins , polysaccharides , glycoproteins , lipoproteins , polypeptides , steroids , analgesics , local anesthetics , antibiotic agents , anti - inflanunatory corticosteroids , ocular drugs and synthetic analogs of these species . examples of drugs which may be delivered by devices according to this invention include , but are not limited to prochlorperzine edisylate , ferrous sulfate , aminocaproic acid , mecamylamine hydrochloride , procainamide hydrochloride , amphetamine sulfate , methamphetamine hydrochloride , benzamphetamine hydrochloride , isoproterenol sulfate , phenmetrazine hydrochloride , bethanechol chloride , methacholine chloride , pilocarpine hydrochloride , atropine sulfate , scopolamine bromide , isopropamide iodide , tridihexethyl chloride , phenformin hydrochloride , methylphenidate hydrochloride , theophylline cholinate , cephalexin hydrochloride , diphenidol , meclizine hydrochloride , prochlorperazine maleate , phenoxybenzamine , thiethylperzine maleate , anisindone , diphenadione erythrityl tetranitrate , digoxin , isoflurophate , acetazolamide , methazolamide , bendroflumethiazide , chloropromaide , tolazamide , chlormadinone acetate , phenaglycodol , allopurinol , aluminum aspirin , methotrexate , acetyl sulfisoxazole , erythromycin , hydrocortisone , hydrocorticosterone acetate , cortisone acetate , dexamethasone and its derivatives such as betamethasone , triamcinolone , methyltestosterone , 17 - s - estradiol , ethinyl estradiol , ethinyl estradiol 3 - methyl ether , prednisolone , 17 -∝- hydroxyprogesterone acetate , 19 - nor - progesterone , norgestrel , norethindrone , norethisterone , norethiederone , progesterone , norgesterone , norethynodrel , aspirin , indomethacin , naproxen , fenoprofen , sulindac , indoprofen , nitroglycerin , isosorbide dinitrate , propranolol , timolol , atenolol , alprenolol , cimetidine , clonidine , imipramine , levodopa , chlorpromazine , methyldopa , dihydroxyphenylalanine , theophylline , calcium gluconate , ketoprofen , ibuprofen , cephalexin , erythromycin , haloperidol , zomepirac , ferrous lactate , vincamine , diazepam , phenoxybenzamine , diltiazem , milrinone , capropril , mandol , quanbenz , hydrochlorothiazide , ranitidine , flurbiprofen , fenufen , fluprofen , tolmetin , alclofenac , mefenamic , flufenamic , difuinal , nimodipine , nitrendipine , nisoldipine , nicardipine , felodipine , lidoflazine , tiapamil , gallopamil , amlodipine , mioflazine , lisinolpril , enalapril , enalaprilat , captopril , ramipril , famotidine , nizatidine , sucralfate , etintidine , tetratolol , minoxidil , chlordiazepoxide , diazepam , amitriptyline , and imipramine . further examples are proteins and peptides which include , but are not limited to , insulin , colchicine , glucagon , thyroid stimulating hormone , parathyroid and pituitary hormones , calcitonin , renin , prolactin , corticotrophin , thyrotropic hormone , follicle stimulating hormone , chorionic gonadotropin , gonadotropin releasing hormone , bovine somatotropin , porcine somatotropin , oxytocin , vasopressin , grf , prolactin , somatostatin , lypressin , pancreozymin , luteinizing hormone , lhrh , lhrh agonists and antagonists , leuprolide , interferons , interleukins , growth hormones such as human growth hormone , bovine growth hormone and porcine growth hormone , fertility inhibitors such as the prostaglandins , fertility promoters , growth factors , coagultion factors , human pancreas hormone releasing factor , analogs and derivatives of these compounds , and pharmaceutically acceptable salts of these compounds , or their analogs or derivatives . on the molecular level , the various forms of the beneficial agent may include uncharged molecules , molecular complexes , and pharmaceutically acceptable acid addition and base addition salts such as hydrochlorides , hydrobromides , acetate , sulfate , laurylate , oleate , and salicylate . for acidic compounds , salts of metals , amines or organic cations may be used . derivatives such as esters , ethers and amides can also be used . a beneficial agent can be used alone or mixed with other agents . the beneficial agent may optionally include pharmaceutically acceptable carriers and / or additional ingredients such as antioxidants , stabilizing agents , permeation enhances , and the like . animals to whom beneficial agents may be administered using systems of this invention include humans and other animals . the invention is of particular interest for application to humans and household , sport , and farm animals , particularly mammals . for the administration of beneficial agents to animals , the devices of the present invention may be implanted subcutaneously or intraperitoneally wherein aqueous body fluids are available to activate the osmotic agent . devices of the invention may also be administered to the rumen of ruminant animals , in which embodiment the devices may further comprise a density element for maintaining the device in the rumen for extended periods of time of up to 120 days or longer . density elements are well known in the art of drug delivery devices . the delivery devices of this invention are also useful in environments outside of physiological or aqueous environments . for example , the delivery devices may be used in intravenous systems ( attached to an iv pump or bag or to an iv bottle , for example ) for delivering beneficial agents to an animal , primarily to humans . they may also be utilized in blood oxygenators , kidney dialysis and electrophoresis , for example . additionally , delivery devices of the present invention may be used in the biotechnology area , such as to deliver nutrients or growth regulating compounds to cell cultures . in such instances , activating mechanisms such as mechanical mechanisms are particularly useful . the beneficial agent may be any of the agents which are known to be delivered to the body of a human or an animal such as medicaments , vitamins , nutrients , or the like . the beneficial agent may also be an agent which is delivered to other types of aqueous environments such as pools , tanks , reservoirs , and the like . included among the types of agents which meet this description are biocides , sterilization agents , nutrients , vitamins , food supplements , sex sterilants , fertility inhibitors and fertility promoters . while the invention has been described in detail with reference to preferred embodiments thereof , it will be apparent to one skilled in the art that various changes can be made , and equivalents employed without departing from the invention .
an osmotic delivery system for controlled delivery of a beneficial agent includes an implant capsule having a beneficial agent reservoir , an osmotic agent which expands on contact with fluid imbibed through a permeable membrane retained by the implant capsule , a delivery port , and a valve for opening and closing the delivery port . when the osmotic agent expands , a pressure is exerted against a separating member positioned between the beneficial agent reservoir and the osmotic agent . the separating member moves within the capsule , thereby forcing the valve to move a distance such that the beneficial agent can exit the reservoir through the delivery port .