Dissolution of Diethazine Hydrochloride from the Coprecipitate with Pectin

抄録

The physical mixture and the coprecipitate of diethazine hydrochloride (DZ), a cationic drug used as a model water-soluble drug, with pectin were studied to determine their dissolution properties in purified water by means of the modified USP dissolution method and the stationary disk method. The release curve of the drug from the physical mixture of DZ and pectin followed the equation already reported by Bamba et al. for the release of a drug from preparations containing a gel-forming excipient. The equation was applicable to the release of the drug from tablets containing up to at least 10% pectin. The apparent dissolution rate from the physical mixture with lactose was significantly larger than that with pectin. The dissolution rate of the physical mixture of DZ and sodium pectate was determined to assess the interference of ionic (Na⁺) interaction with the release of the drug from DZ/pectin coprecipitate. The initial dissolution rate from the physical mixture with sodium pectate was larger than that from the physical mixture with pectin or from the coprecipitate, but was very small compared with that of the intact drug, suggesting that the interference of Na⁺ with the dissolution is small. The initial apparent dissolution rate from the physical mixture with pectin, at a short time after initiation, was almost the same as that from the coprecipitate (complex). These results suggest that cationic water-soluble drugs may be formulated as sustainedrelease preparations by adding a small amount of pectin, owing to the gel-forming ability of pectin and the complex formation between the drug and pectin in aqueous solution.