Mechanism of Optical Isomerization of(S)-N-[1-(2-Fluorophenyl)-3,4,6,7-tetrahydro-4-oxopyrrolo[3,2,1-jk] [l,4]-benzodiazepine-3-y1]-1H-indole-2-carboxamide (FK480) in Soft Capsules Containing Polyethylene Glycol 400 and Glycerol