Interaction of Phenothiazines with Pectin in the Solid State

Abstract

The interaction of phenothiazines with pectin in the solid state was investigated, and the formation of coprecipitates was confirmed by infrared absorption spectroscopy and powder X-ray diffractometry. There was a positive correlation between the amount of drug in the coprecipitate and the primary binding number n₁ of phenothiazines with pectin in aqueous solution. The initial dissolution rate of drug from the coprecipitates in purified water followed zero-order kinetics and was very small compared with that of the intact drug. The dissolution rate of diethazine/pectin coprecipitate was almost independent of the rotating speed in 0.1 N hydrochloric acid. These results suggest that coprecipitates of drugs with pectin might be useful as sustained-release preparations.