Dissolution mechanisms of drug-polyvinylpyrrolidone coprecipitates in aqueous solution.

Abstract

Coprecipitates of sulfamethizole-polyvinylpyrrolidone (PVP) and sulfisoxazole-PVP were prepared at various ratios. The dissolution rates of the drugs in the coprecipitates were greater when the ratio of drug to PVP was smaller. The dissolution rate of sulfamethizole in the coprecipitate was greater when PVP of smaller molecular weight was used. Dissolution patterns were different for sulfamethizole-PVP coprecipitate and sulfisoxazole-PVP coprecipitate ; recrystallization of the drug was observed following the dissolution of sulfisoxazole-PVP coprecipitate, whereas no recrystallization was found in the dissolution of sulfamethizole-PVP coprecipitate. A new dissolution model for coprecipitate is proposed.