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Claims for Patent: 4,652,441

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Claims for Patent: 4,652,441

Title: Prolonged release microcapsule and its production
Abstract:A microcapsule produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing said water-soluble drug and a drug retaining substance therefor and an oil layer containing a polymer substance, then thickening or solidifying said inner aqueous layer to a viscosity of not lower than about 5000 centiposes and finally subjecting the resulting emulsion to in water drying gives prolonged release of water-soluble drug.
Inventor(s): Okada; Hiroaki (Suita, JP), Ogawa; Yasuaki (Ibaraki, JP), Yashiki; Takatsuka (Takarazuka, JP)
Assignee: Takeda Chemical Industries, Ltd. (Osaka, JP)
Application Number:06/667,096
Patent Claims: 1. A prolonged release microcapsule having an average diameter of about 2 to 200.mu.m for injection, which is produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing a biologically active polypeptide, a drug retaining substance therefor selected from a member of the group consisting of gelatin, albumin, pectin and agar and an oil layer containing a polymer substance of lactic acid-glycolic acid copolymer or lactic acid polymer, then thickening or solidifying said inner aqueous layer to a viscosity of not lower than about 5000 centipoises and finally admixing the resulting emulsion with a third aqueous layer to give a water/oil/water ternary layer emulsion and then desorbing the solvent in the oil layer.

2. A microcapsule as claimed in claim 1, wherein the biologically active polypeptide is (Pyr) Glu-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-Pro-NH-C.sub.2 H.sub.5.

3. A microcapsule as claimed in claim 1, wherein the drug retaining substance is gelatin.

4. A microcapsule as claimed in claim 1, wherein the polymer substance in the oil layer is a copolymer of lactic acid and glycolic acid.

5. A microcapsule as claimed in claim 4, wherein the ratio of lactic acid:glycolic acid is 75:25.

6. A microcapsule as claimed in claim 1, wherein the polymer substance in the oil layer is polylactic acid.

7. A microcapsule as claimed in claim 1, wherein the inner aqueous layer is thickened to a viscosity not less than about 10,000 centipoises.

8. A microcapsule as claimed in claim 1, wherein the inner aqueous layer is solidified.

9. A method for producing a prolonged release microcapsule having an average diameter of about 2 to 200 .mu.m for injection, which comprises preparing a water-in-oil emulsion comprising an inner aqueous layer containing a biologically active polypeptide, a drug retaining substance therefor selected from a member of the group consisting of gelatin, albumin, pectin and agar and an oil layer containing a polymer substance of lactic acid-glycolic acid copolymer or lactic acid polymer, then thickening or solidifying said inner aqueous layer to a viscosity of not lower than about 5000 centipoises and finally admixing the resulting emulsion with a third aqueous layer to give a water/-oil/water ternary layer emulsion and then desorbing the solvent in the oil layer.
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