Preparations of Solid Particulates of Amino-Pyrine-Barbital Complex (Pyrabital) wiithout Autoxidation Ey a Spray Drying Technique

Abstract

Aminopyrine, barbital and colloidal silica dispersed in buffer solutions having pH 5.46 to 8.01 were spray-dried by a centrifugal wheel atomizer at 130 ± 5°C. When the pH of the feeding liquid for spray drying was 5.70 to 7.24, the resultant product was a mixture of amlnopyrine-barbital complex (pyrabital), aminopyrine and the exci-pient. When the pH was lower than 5.84 or higher than 7.84, barbital or sodium barbital coexisted in the above mixture products. Autoxidation of aminopyrine occurred during the spray drying was greatly prevented by introducing chelating agent, e.g. ethylenediaminetetraacetic acid and glycine, or antioxidation agent, e.g. sodium thiosulfate and citric acid in the feeding liquid. It was also found that reducing the pH of the feeding liquid effectively depressed the autoxidation of aminopyrine.