Claims for Patent: 5,330,767

Summary for Patent: 5,330,767

Title:	Sustained release microcapsule
Abstract:	Microcapsules are advantageously produced with high take-up of a water-soluble drug by preparing a W/O emulsion composed of a water-soluble drug-containing solution as the inner aqueous phase and a polymer-containing solution as the oil phase, dispersing said emulsion in an aqueous phase and subjecting the resulting W/O/W emulsion to an in-water drying, wherein the viscosity of the W/O emulsion used in preparing the W/O/W emulsion is adjusted to about 150 to about 10,000 centipoises.
Inventor(s):	Yamamoto; Masaki (Osaka, JP), Takada; Shigeyuki (Osaka, JP), Ogawa; Yasuaki (Osaka, JP)
Assignee:	Takeda Chemical Industries, Ltd. (Osaka, JP)
Application Number:	07/936,726
Patent Claims:	1. A sustained-release microcapsule for injection containing a water-soluble drug, which is produced by a process consisting essentially of preparing a W/O emulsion composed of a water-soluble drug-containing solution as the inner aqueous phase and a biodegradable polymer-containing solution as the oil phase, adjusting the viscosity of the W/O emulsion used in preparing the W/O/W emulsion to from about 150 to about 10,000 centipoises by the procedures of increasing the polymer concentration in the oil phase; adjusting the ratio of the aqueous phase to the oil phase; adjusting the temperature of said W/O emulsion; adjusting the temperature of the external aqueous phase; adjusting the temperature of the W/O emulsion with a line heater or cooler or the like in infusing the W/O emulsion into the external aqueous phase; or carrying out the above procedures in combination, dispersing said emulsion in an aqueous phase and subjecting the resulting W/O/W emulsion to an in-water drying to form microcapsules. 2. A microcapsule as claimed in claim 1, wherein the viscosity of the W/O emulsion in preparing the W/O/W emulsion is adjusted to about 150 to 5,000 centipoises. 3. A microcapsule as claimed in claim 1, wherein the viscosity of the W/O emulsion in preparing the W/O/W emulsion is adjusted to about 150 to about 10,000 centipoises by the manner of regulating the temperatures of (i) the W/O emulsion or (ii) both the W/O emulsion and the external aqueous phase to from about -20.degree. C. to the boiling point of the organic solvent used. 4. A microcapsule as claimed in claim 3, wherein the temperature is about 0.degree. C. to 30.degree. C. 5. A microcapsule as claimed in claim 1, wherein the polymer concentration in the oil phase is increased to about 10 to 80% 6. A microcapsule as claimed in claim 1, wherein the ratio of the aqueous phase to the oil phase is adjusted to the range of about 1% to 50%. 7. A microcapsule as claimed in claim 1, wherein the water-soluble drug is a biologically active polypeptide. 8. A microcapsule as claimed in claim 7, wherein the biologically active polypeptide is (Pyr)Glu-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-Pro-NH-C.sub.2 H.sub.5.acetate. 9. A microcapsule as claimed in claim 1, wherein the polymer is polylactic acid. 10. A microcapsule as claimed in claim 1, wherein the polymer is a copolymer of lactic acid and glycolic acid. 11. A microcapsule as claimed in claim 10, wherein the ratio of lactic acid: glycolic acid of the copolymer is about 75.+-.2 mole %: about 25.+-.2 mole %. 12. A microcapsule as claimed in claim 1, wherein the in-water drying is conducted by allowing the W/O/W emulsion to stand under stirring. 13. A microcapsule as claimed in claim 1, wherein the in-water drying is conducted by gradually reducing the pressure while stirring with a propeller-shaped stirrer, magnetic stirrer or rotary evaporator.