Soft-gelatin capsule formulation

1. A soft gelatin capsule formulation of a 15-keto-prostaglandin compound, which comprises:

a soft gelatin capsule shell comprising gelatin and sugar alcohol as a sole plasticizer, and

a mixture comprising a 15-keto-prostaglandin compound and a pharmaceutically acceptable vehicle, which is filled in the shell.

2. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a compound of the formula (I):

wherein L, M and N are hydrogen, hydroxy, halogen, lower alkyl, hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein at least one of L and M is a group other than hydrogen, and the five-membered ring may have at least one double bond;

A is —CH 3 , or —CH 2 OH, —COCH 2 OH, —COOH or a functional derivative thereof;

B is —CH 2 —CH 2 —, —CH═CH— or —C≡C—;

R 1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, lower alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur; and

Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or heterocyclicoxy group; lower alkoxy; lower alkanoyloxy; cyclo(lower)alkyl; cyclo(lower)alkyloxy; aryl; aryloxy; heterocyclic group; heterocyclicoxy group.

3. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 13,14-dihydro-15-keto-prostaglandin compound.

4. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 15-keto-16-mono or 16,16-di-halogen-prostaglandin compound.

5. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 13,14-dihydro-15-keto-16-mono- or 16,16-di-halogen-prostaglandin compound.

6. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 15-keto-16-mono- or 16,16-di-fluoro-prostaglandin compound.

7. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 13,14-dihydro-15-keto-16-mono- or 16,16-di-fluoro-prostaglandin compound.

8. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 15-keto-prostaglandin E compound.

9. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 13,14-dihydro-15-keto-16,16-difluoro-prostaglandin E 1 .

10. The formulation of claim 1 , wherein the 15-keto-prostaglandin compound is a 13,14-dihydro-15-keto-16,16-difluoro-18S-methyl-prostaglandin E 1 .

11. The formulation of claim 1 , wherein the pharmaceutically acceptable vehicle is a fatty acid ester or a polyol.

12. The formulation of claim 1 , wherein the fatty acid ester is a glyceride.

13. The formulation of claim 1 , wherein the sugar alcohol is selected from the group consisting of sorbitol, maltitol, sugar alcohol solution derived from corn starch, hydrogenated maltose syrup and a mixture thereof.

14. The formulation of claim 1 , wherein the sugar alcohol comprises sorbitol and sorbitan as its major component.

15. A method for stabilizing a 15-keto-prostaglandin compound, which comprises: dissolving, dispersing or mixing the 15-keto-prostaglandin in a pharmaceutically acceptable vehicle to give a liquid mixture, and incorporating the liquid mixture in a soft gelatin capsule which comprises gelatin and sugar alcohol as a sole plasticizer.

16. The method of claim 15 , wherein the sugar alcohol is selected from the group consisting of sorbitol, maltitol, sugar alcohol solution derived from corn starch, hydrogenated maltose syrup and a mixture thereof.

17. The method of claim 15 , wherein the sugar alcohol comprises sorbitol and sorbitan as its major component.