Molecular interaction between E-prostaglandins and selected polymers and its potential utilization in oral dosage form design

Coacervate formation was observed between some E-prostaglandins and povidone in acetonitrile. This molecular interaction was studied using differential scanning calorimetry, IR spectrophotometry, and light microscopy. The structural requirements for coacervate formation between E-prostaglandins and povidone were investigated. Possible utilization of this molecular interaction in the development of E-prostaglandin formulations was explored. The dissolution rate of some insoluble E-prostaglandin esters increased when they were coprecipitated with povidone and polyethylene glycol. For example, the p-hydroxybenzaldehyde semicarbazone ester of 16,16-dimethyldinoprostone dissolved about 200 times faster as a povidone coprecipitate than did the control mixture. Enhancement of the dissolution rate was observed for the povidone coprecipitates of dinoprostone and its p-acetylphenyl and beta-naphthyl exters but not for the p-phenylphenyl ester. Fast dissolving dispersions of the E-prostaglandin esters also could be prepared with the water-insoluble cross-linked polyvinylpyrrolidone. This type of dispersion was nonglassy and easily dispersible in water. Thus, it might have certain advantages over the classical soluble povidone coprecipitates in terms of ease of handling. The degree of enhancement in dissolution of dispersions of cross-linked polyvinylpyrrolidone and E-prostaglandin esters is apparently dependent on the structure of the esters. The potential dissolution enhancement may be related to the strength of the interaction between the macromolecule and the esters, as indicated by the qualitative relationship between the extent of adsorption of the prostaglandins to cross-linked polyvinylpyrrolidone and the dissolution rate enhancement.