Dissolution behaviors and gastrointestinal absorption of tolbutamide in tolbutamide-polyvinylpyrrolidone coprecipitate.

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Abstract
Coprecipitates were prepared in various ratios of tolbutamide-polyvinylpyrrolidone (PVP). The X-ray diffraction spectra indicated that tolbutamide in the coprecipitate did not exhibit its crystalline property. Comparative studies were made on the in vitro dissolution and the in vivo absorption of tolbutamide from the coprecipitate and the drug alone. The dissolution rate of tolbutamide was markedly increased in the tolbutamide PVP coprecipitates in the pharmacopeial disintegration media at pH 1.2 and 7.5. In vivo absorption study of each preparation was carried out by determining the plasma level of tolbutamide following the oral administration to rabbits. Bioavailability of tolbutamide was improved in the coprecipitate 1.37 times as much as tolbutamide alone. The drug was rapidly and completely absorbed following oral administration of coprecipitate. Quantitative analysis of PVP in the solution was also studied by the determination of the fluorescence of the complex of PVP and 8-anilino-1-naphthalene-sulfonic acid sodium salt. [Tolbutamide is an oral hypoglycemic drug used in the treatment of diabetes.].