Inclusion complexation of prostaglandin F2 alpha with gamma-cyclodextrin in solution and solid phases

A solid complex of prostaglandin F2 alpha (dinoprost) with gamma-cyclodextrin in a molar ratio of 1:1 was obtained on the basis of the BS-type phase solubility diagram. The mode of interaction in the solid state was studied by powder X-ray diffractometry, thermal analysis, and carbon-13 cross polarization/magic angle spinning nuclear magnetic resonance (13C-CP/MAS-NMR) spectrometry. The X-ray diffraction and NMR data suggested that prostaglandin F2 alpha is included in the cylindrical channels formed by coaxial alignment of gamma-cyclodextrin molecules to give a channel type structure. Dissolution and thermal behaviors of the prostaglandin F2 alpha-gamma-cyclodextrin complex were examined and compared with the drug itself. The result indicated that the gamma-cyclodextrin complex may have great utility as a rapidly dissolving form of prostaglandin F2 alpha with improved thermal stability.