Claims for Patent: 6,340,475

Summary for Patent: 6,340,475

Title:	Extending the duration of drug release within the stomach during the fed mode
Abstract:	Drugs are formulated as unit oral dosage forms by incorporating them into polymeric matrices comprised of hydrophilic polymers that swell upon imbibition of water to a size that is large enough to promote retention of the dosage form in the stomach during the fed mode. The oral formulation is designed for gastric retention and controlled delivery of an incorporated drug into the gastric cavity, and thus administered, the drug is released from the matrix into the gastric fluid by solution diffusion. The swollen polymeric matrix, having achieved sufficient size, remains in the gastric cavity for several hours if administered while the patient is in the fed mode, and remains intact long enough for substantially all of the drug to be released before substantial dissolution of the matrix occurs. The swelling matrix lowers the accessibility of the gastric fluid to the drug and thereby reduces the drug release rate. This process, together with diffusion retardation by selection of specific polymers, polymer molecular weights, and other variables, results in a sustained and controlled delivery rate of the drug to the gastric cavity.
Inventor(s):	Shell; John W. (Hillsborough, CA), Louie-Helm; Jenny (Union City, CA), Markey; Micheline (Santa Cruz, CA)
Assignee:	DepoMed, Inc. (Menlo Park, CA)
Application Number:	09/282,233
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 6,340,475
Patent Claims:	1. A controlled-release oral drug dosage form for releasing a drug whose solubility in water is greater than one part by weight of said drug in ten parts by weight of water, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 15:85 to about 80:20, said polymeric matrix being one that swells upon imbibition of water thereby attaining a size large enough to promote retention in the stomach during said fed mode, that releases said drug into gastric fluid by the dissolution and diffusion of said drug out of said matrix by said gastric fluid, that upon immersion in gastric fluid retains at least about 40% of said drug one hour after such immersion and releases substantially all of said drug within about eight hours after such immersion, and that remains substantially intact until all of said drug is released. 2. A dosage form of claim 1 in which the solubility of said drug in water is greater than one part by weight of said drug in five parts by weight of water. 3. A dosage form of claim 1 in which said drug is a member selected from the group consisting of metformin hydrochloride, vancomycin hydrochloride, captopril, erythromycin lactobionate, ranitidine hydrochloride, sertraline hydrochloride, tramadol and ticlopidine hydrochloride. 4. A dosage form of claim 1 in which said drug is metformin hydrochloride. 5. A dosage form of claim 1 in which said drug is sertraline hydrochloride. 6. A dosage form of claim 1 in which said drug is captopril. 7. A dosage form of claim 1 in which said drug is vancomycin hydrochloride. 8. A dosage form of claim 1 in which said polymeric matrix is formed of a polymer selected from the group consisting of poly(ethylene oxide), cellulose, alkyl-substituted celluloses, crosslinked polyacrylic acids, and xanthan gum. 9. A dosage form of claim 8 in which said alkyl-substituted celluloses are members selected from the group consisting of hydroxymethyl-cellulose, hydroxyethyl-cellulose, hydroxypropyl-cellulose, hydroxypropylmethyl-cellulose, and carboxymethyl-cellulose. 10. A dosage form of claim 1 in which said polymeric matrix is formed of poly(ethylene oxide) at a molecular weight of at least about 4,000,000. 11. A dosage form of claim 1 in which said polymeric matrix is formed of poly(ethylene oxide) at a molecular weight in the range of about 4,500,000 to about 10,000,000. 12. A dosage form of claim 1 in which said polymeric matrix is formed of poly(ethylene oxide) at a molecular weight in the range of about 5,000,000 to about 8,000,000. 13. A dosage form of claim 1 in which said polymeric matrix upon immersion in gastric fluid retains at least about 50% of said drug one hour after such immersion. 14. A dosage form of claim 1 in which said polymeric matrix upon immersion in gastric fluid retains at least about 60% of said drug one hour after such immersion. 15. A dosage form of claim 1 in which said polymeric matrix upon immersion in gastric fluid retains at least about 80% of said drug one hour after such immersion. 16. A dosage form of claim 1 further comprising a member selected from the group consisting of glyceryl monostearate and sodium myristate, formulated with said drug to further retard the release of said drug to said gastric fluid. 17. A dosage form of claim 1 in which said polymeric matrix consists of two cylindrical tablets, each measuring about 9 mm to about 12 mm in length and about 6.5 mm to about 7 mm in diameter. 18. A dosage form of claim 1 in which said polymeric matrix consists of a single elongated tablet measuring about 18 mm to about 22 mm in length, about 6.5 mm to about 7.8 mm in width, and about 6.2 to 7.5 mm in height. 19. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach and doing so in a manner that substantially avoids the alteration of intestinal flora that said drug otherwise tends to cause, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach and substantially avoiding contact of said drug with said intestinal flora. 20. A method in accordance with claim 19 in which said drug is a member selected from the group consisting of amoxicillin, cefuroxime axetil, cefaclor, clindamycin, clarithromycin, azithromycin, ceftazidine, and ciprofloxacin. 21. A method in accordance with claim 19 in which said drug is a highly soluble drug selected from the group consisting of amoxicillin, cefuroxime axetil, cefaclor, and clindamycin. 22. A method of treating a subject suffering from infections selected from the group consisting of pneumonia, sinus bacterial infections, topical bacterial infections and staphylococcus infections, by administering to said subject a drug which is a member selected from the group consisting of amoxicillin, cefuroxime axetil, cefaclor, clindamycin, clarithromycin, azithromycin, and ceftazidine, without substantially causing side effects resulting from the alteration of the intestinal flora of said subject, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach and substantially avoiding contact of said drug with said intestinal flora. 23. A method in accordance with claim 22 in which said drug is a highly soluble drug selected from the group consisting of amoxicillin, cefuroxime axetil, cefaclor, and clindamycin. 24. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach but also degradable by colonic bacterial enzymes residing in lower gastrointestinal tract enterocytes, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach and substantially avoiding contact of said drug with said intestinal enzymes and said drug transporters. 25. A method in accordance with claim 24 in which said drug is a member selected from the group consisting of cyclosporine, digoxin, and doxifluridine. 26. A method in accordance with claim 24 in which said drug is doxifluridine. 27. A method of treating a subject undergoing an organ transplant to suppress an immune response to said transplant, by administering cyclosporine to said subject without substantial degradation of said cyclosporine by colonic bacterial enzymes residing in enterocytes of the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said cyclosporine while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said cyclosporine dispersed therein at a weight ratio of cyclosporine to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said cyclosporine one hour after such immersion in gastric fluid, (d) releases substantially all of said cyclosporine within about ten hours after such immersion, and (e) remains substantially intact until all of said cyclosporine is released, thereby extending the release rate of said cyclosporine with time during said fed mode while releasing substantially all of said cyclosporine within said stomach and substantially avoiding contact of said cyclosporine with said colonic bacterial enzymes. 28. A method of treating a subject for heart disease by administering digoxin to said subject without substantial degradation of said digoxin by colonic bacterial enzymes residing in enterocytes of the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said digoxin while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said digoxin dispersed therein at a weight ratio of digoxin to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said digoxin one hour after such immersion in gastric fluid, (d) releases substantially all of said digoxin within about ten hours after such immersion, and (e) remains substantially intact until all of said digoxin is released, thereby extending the release rate of said digoxin with time during said fed mode while releasing substantially all of said digoxin within said stomach and substantially avoiding contact of said digoxin with said colonic bacterial enzymes. 29. A method of treating a subject suffering from a condition selected from the group consisting of ovarian cancer, colorectal cancer, gastric cancer, renal cancer, and breast cancer, by administering doxifluridine to said subject without substantial degradation of said doxifluridine by intestinal enzymes or substantial inactivation of said doxifluridine by drug transporters residing in enterocytes of the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said doxifluridine while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said doxifluridine dispersed therein at a weight ratio of doxifluridine to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said doxifluridine one hour after such immersion in gastric fluid, (d) releases substantially all of said doxifluridine within about ten hours after such immersion, and (e) remains substantially intact until all of said doxifluridine is released, thereby extending the release rate of said doxifluridine with time during said fed mode while releasing substantially all of said doxifluridine within said stomach and substantially avoiding contact of said doxifluridine with said enzymes. 30. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach but also susceptible to inactivation by drug transporters residing in lower gastrointestinal tract enterocytes, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach and substantially avoiding contact of said drug with said drug transporters. 31. A method in accordance with claim 30 in which said drug is a member selected from the group consisting of cyclosporine and paclitaxel. 32. A method of treating a subject undergoing an organ transplant to suppress an immune response to said transplant, by administering cyclosporine to said subject without substantial inactivation of said cyclosporine by p-glycoprotein in the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said cyclosporine while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said cyclosporine dispersed therein at a weight ratio of cyclosporine to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said cyclosporine one hour after such immersion in gastric fluid, (d) releases substantially all of said cyclosporine within about ten hours after such immersion, and (e) remains substantially intact until all of said cyclosporine is released, thereby extending the release rate of said cyclosporine with time during said fed mode while releasing substantially all of said cyclosporine within said stomach and substantially avoiding inactivation of said cyclosporine by p-glycoprotein in said lower gastrointestinal tract. 33. A method of treating a subject suffering from cancer by administering paclitaxel to said subject without substantial inactivation of said paclitaxel by p-glycoprotein in the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said paclitaxel while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said paclitaxel dispersed therein at a weight ratio of paclitaxel to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said paclitaxel one hour after such immersion in gastric fluid, (d) releases substantially all of said paclitaxel within about ten hours after such immersion, and (e) remains substantially intact until all of said paclitaxel is released, thereby extending the release rate of said paclitaxel with time during said fed mode while releasing substantially all of said paclitaxel within said stomach and substantially avoiding inactivation of said paclitaxel by p-glycoprotein in said lower gastrointestinal tract. 34. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach and whose bioavailability is substantially greater in an acidic environment than an alkaline environment, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach where said drug is maintained in an acidic environment. 35. A method in accordance with claim 34 in which said drug is a member selected from the group consisting of esters of ampicillin, iron salts, digoxin, and ketoconazole. 36. A method in accordance with claim 34 in which said drug is a member selected from the group consisting of esters of ampicillin. 37. A method of treating a subject suffering from a bacterial infection by administering an ester of ampicillin to said subject while maintaining maximum bioavailability of said ester of ampicillin, said method comprising orally administering to said subject a dosage form of said ester of ampicillin while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said ester of ampicillin dispersed therein at a weight ratio of said ester of ampicillin to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said ester of ampicillin one hour after such immersion in gastric fluid, (d) releases substantially all of said ester of ampicillin within about ten hours after such immersion, and (e) remains substantially intact until all of said ester of ampicillin is released, thereby extending the release rate of said ester of ampicillin with time during said fed mode while releasing substantially all of said ester of ampicillin within said stomach and maintaining said ester of ampicillin in the acidic environment of said stomach during said release. 38. A method of treating a subject suffering from anemia by administering iron salts to said subject while maintaining maximum bioavailability of said iron salts, said method comprising orally administering to said subject a dosage form of said iron salts while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said iron salts dispersed therein at a weight ratio of iron salts to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said iron salts one hour after such immersion in gastric fluid, (d) releases substantially all of said iron salts within about ten hours after such immersion, and (e) remains substantially intact until all of said iron salts is released, thereby extending the release rate of said iron salts with time during said fed mode while releasing substantially all of said iron salts within said stomach where said iron salts are maintained in an acidic environment. 39. A method of treating a subject suffering from a systemic fungal infection by administering ketoconazole to said subject while maintaining maximum bioavailability of said ketoconazole, said method comprising orally administering to said subject a dosage form of said ketoconazole while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said ketoconazole dispersed therein at a weight ratio of ketoconazole to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said ketoconazole one hour after such immersion in gastric fluid, (d) releases substantially all of said ketoconazole within about ten hours after such immersion, and (e) remains substantially intact until all of said ketoconazole is released, thereby extending the release rate of said ketoconazole with time during said fed mode while releasing substantially all of said ketoconazole within said stomach where said ketoconazole is maintained in an acidic environment. 40. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach but also degradable in an alkaline environment, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix in which said drug is dispersed at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach where said drug is maintained in an acidic environment. 41. A method in accordance with claim 40 in which said drug is nelfinar mesylate. 42. A method of treating a subject infected with human immunodeficiency virus by administering nelfinar mesylate to said subject without substantial degradation of said nelfinar mesylate by intestinal flora or substantial inactivation of said nelfinar mesylate by drug transporters residing in enterocytes of the lower gastrointestinal tract, said method comprising orally administering to said subject a dosage form of said nelfinar mesylate while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said nelfinar mesylate dispersed therein at a weight ratio of nelfinar mesylate to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said nelfinar mesylate into gastric fluid by the dissolving of said nelfinar mesylate by said gastric fluid and either erosion of said matrix or diffusion of said dissolved nelfinar mesylate out of said matrix, (c) retains at least about 40% of said nelfinar mesylate one hour after such immersion in gastric fluid, (d) releases substantially all of said nelfinar mesylate within about ten hours after such immersion, and (e) remains substantially intact until all of said nelfinar mesylate is released, thereby extending the release rate of said nelfinar mesylate with time during said fed mode while releasing substantially all of said nelfinar mesylate within said stomach where said nelfinar mesylate is maintained in an acidic environment. 43. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach where said drug has at least one ionized group in the pH range 5 through 8, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (d) releases substantially all of said drug within about ten hours after such immersion, and (e) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach where said drug is maintained in an acidic environment. 44. A method of administering to a subject a drug that is therapeutic to said subject when absorbed in the stomach but also degradable in an acidic environment, said method comprising orally administering to said subject a dosage form of said drug while said subject is in a fed mode, said dosage form comprising a solid polymeric matrix with said drug dispersed therein at a weight ratio of drug to polymer of from about 0.01:99.99 to about 80:20, said polymeric matrix being one that: (a) swells upon imbibition of gastric fluid to a size large enough to promote retention in the stomach during said fed mode, (b) releases said drug into gastric fluid by the dissolving of said drug by said gastric fluid and either erosion of said matrix or diffusion of said dissolved drug out of said matrix, (c) protects any unreleased drug in said matrix from said gastric fluid, (d) retains at least about 40% of said drug one hour after such immersion in gastric fluid, (e) releases substantially all of said drug within about ten hours after such immersion, and (f) remains substantially intact until all of said drug is released, thereby extending the release rate of said drug with time during said fed mode while releasing substantially all of said drug within said stomach where said drug is maintained in an acidic environment. 45. A dosage form of claim 1 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises an alkyl-substituted cellulose. 46. A dosage form of claim 1 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises hydroxypropylmethyl cellulose. 47. A dosage form of claim 1 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of from about 4,500,000 to about 10,000,000. 48. A method in accordance with claim 19 in which said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of at least about 4,000,000. 49. A method in accordance with claim 19 in which said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of from about 4,500,000 to about 10,000,000. 50. A method in accordance with claim 19 in which said solid polymeric matrix comprises an alkyl-substituted cellulose. 51. A method in accordance with claim 19 in which said solid polymeric matrix comprises hydroxypropylmethyl cellulose. 52. A method in accordance with claim 43 in which said drug is a member selected from the group consisting of metformin hydrochloride, lisinopril, captopril, buproprion, ganciclovir, and iron salts. 53. A method in accordance with claim 43 in which said drug is metformin hydrochloride. 54. A method in accordance with claim 43 in which said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of at least about 4,000,000. 55. A method in accordance with claim 43 in which said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of from about 4,500,000 to about 10,000,000. 56. A method in accordance with claim 43 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises poly(ethylene oxide) at a molecular weight of at least about 4,000,000. 57. A method in accordance with claim 43 in which said solid polymeric matrix comprises an alkyl-substituted cellulose. 58. A method in accordance with claim 43 in which said solid polymeric matrix comprises hydroxypropylmethyl cellulose. 59. A method in accordance with claim 43 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises an alkyl-substituted cellulose. 60. A method in accordance with claim 43 in which said drug is metformin hydrochloride and said solid polymeric matrix comprises hydroxypropylmethyl cellulose. 61. A dosage form of claim 1 in which said polymeric matrix is comprised of hydroxypropylmethylcellulose. 62. A dosage form of claim 1 in which said polymeric matrix is comprised of hydroxypropylmethylcellulose with a viscosity range of 11,000 to 110,000 centipoise as measured in a 2% solution at 20.degree. C. 63. A dosage form of claim 1 in which said drug is metformin hydrochloride and said polymeric matrix is comprised of hydroxypropylmethylcellulose with a viscosity range of 11,000 to 110,000 centipoise as measured in a 2% solution at 20.degree. C. 64. A dosage form of claim 1 in which said drug is metformin hydrochloride and said polymeric matrix is comprised of an alkyl-substituted cellulose. 65. A dosage form of claim 1 in which said drug is metformin hydrochloride and said polymeric matrix is comprised of hydroxypropylmethylcellulose. 66. A method in accordance with claim 43 in which said polymeric matrix is comprised of hydroxypropylmethylcellulose with a viscosity range of 11,000 to 110,000 centipoise as measured in a 2% solution at 20.degree. C. 67. A method in accordance with claim 43 in which said drug is metformin hydrochloride and said polymeric matrix is comprised of hydroxypropylmethylcellulose with a viscosity range of 11,000 to 110,000 centipoise as measured in a 2% solution at 20.degree. C. 68. A controlled-release oral drug dosage form for releasing metformin hydrochloride, said dosage form comprising a solid polymeric matrix with said metformin hydrochloride therein at a weight ratio of drug to polymer of from about 15:85 to about 80:20, said polymeric matrix being one that swells upon imbibition of water thereby attaining a size large enough to promote retention in the stomach during the fed mode, that releases said metformin hydrochloride into gastric fluid by the dissolution and diffusion of said metformin hydrochloride out of said matrix by said gastric fluid, and that upon immersion in gastric fluid retains at least about 40% of said metformin hydrochloride one hour after such immersion. 69. The dosage form of claim 68, wherein said polymeric matrix comprises a polymer selected from the group consisting of poly(ethylene oxide), cellulose, alkyl-substituted celluloses, crosslinked polyacrylic acids, and xanthum gum. 70. The dosage form of claim 69, wherein said polymeric matrix comprises an alkyl-substituted cellulose. 71. The dosage form of claim 70, wherein said polymeric matrix comprises an alkyl-substituted cellulose selected from the group consisting of hydroxymethyl-cellulose, hydroxyethyl-cellulose, hydroxypropyl-cellulose, hydroxypropylmethyl-cellulose, and carboxymethyl-cellulose. 72. The dosage form of claim 71, wherein said polymeric matrix comprises hydroxypropylmethyl-cellulose. 73. The dosage form of claim 71, wherein said polymeric matrix comprises hydroxypropylmethyl-cellulose having a viscosity ranging from 11,000 to 110,000 centipoise as measured in a 2% solution at 20 C. 74. The dosage form of claim 68, wherein said polymeric matrix upon immersion in gastric fluid retains at least about 50% of said metformin hydrochloride one hour after such immersion. 75. The dosage form of claim 68, wherein said polymeric matrix upon immersion in gastric fluid retains at least about 60% of said metformin hydrochloride one hour after such immersion. 76. The dosage form of claim 68, wherein said polymeric matrix comprises poly(ethylene oxide) having a molecular weight of at least about 4,000,000. 77. The dosage form of claim 68, wherein said polymeric matrix comprises poly(ethylene oxide) having a molecular weight ranging from about 4,500,000 to about 10,000,000. 78. The dosage form of claim 68, wherein said polymeric matrix comprises poly(ethylene oxide) having a molecular weight ranging from about 5,000,000 to about 8,000,000. 79. A controlled-release oral drug dosage form for releasing metformin hydrochloride, said dosage form comprising a solid polymeric matrix tablet with said metformin hydrochloride therein at a weight ratio of drug to polymer of from about 15:85 to about 80:20, said polymeric matrix tablet being one that swells upon imbibition of water thereby attaining a size large enough to promote retention in the stomach during the fed mode, that releases said metformin hydrochloride into gastric fluid by the dissolution and diffusion of said metformin hydrochloride out of said matrix by said gastric fluid, and that upon immersion in gastric fluid retains at least about 40% of said metformin hydrochloride one hour after such immersion. 80. The dosage form of claim 79, wherein said polymeric matrix of said polymeric matrix tablet comprises a polymer selected from the group consisting of poly(ethylene oxide), cellulose, alkyl-substituted celluloses, crosslinked polyacrylic acids, and xanthum gum. 81. The dosage form of claim 80, wherein said polymeric matrix comprises an alkyl-substituted cellulose. 82. The dosage form of claim 81, wherein said polymeric matrix comprises an alkyl-substituted cellulose selected from the group consisting of hydroxymethyl-cellulose, hydroxyethyl-cellulose, hydroxypropyl-cellulose, hydroxypropylmethyl-cellulose, and carboxymethyl-cellulose. 83. The dosage form of claim 82, wherein said polymeric matrix comprises hydroxypropylmethyl-cellulose. 84. The dosage form of claim 83, wherein said polymeric matrix comprises hydroxypropylmethyl-cellulose having a viscosity ranging from 11,000 to 110,000 centipoise as measured in a 2% solution at 20 C. 85. The dosage form of claim 79, wherein said polymeric matrix tablet upon immersion in gastric fluid retains at least about 50% of said metformin hydrochloride one hour after such immersion. 86. The dosage form of claim 79, wherein said polymeric matrix tablet upon immersion in gastric fluid retains at least about 60% of said metformin hydrochloride one hour after such immersion. 87. The dosage form of claim 79, wherein said polymeric matrix of said polymeric matrix tablet comprises poly(ethylene oxide) having a molecular weight of at least about 4,000,000. 88. The dosage form of claim 79, wherein said polymeric matrix of said polymeric matrix tablet comprises poly(ethylene oxide) having a molecular weight ranging from about 4,500,000 to about 10,000,000. 89. The dosage form of claim 79, wherein said polymeric matrix of said polymeric matrix tablet comprises poly(ethylene oxide) having a molecular weight ranging from about 5,000,000 to about 8,000,000.