Bioavailability and Dissolution Behavior of Trisulfapyrimidine Suspensions

The bioavailability of seven commercial trisulfapyrimidine suspensions was studied in 14 adult male volunteers. Fifteen blood samples were collected over a 48‐hr period following administration of a 1‐g dose of each suspension. Serum was assayed for each component, (sulfadiazine, sulfamerazine, and sulfamethazine) by high‐pressure liquid chromatography. Analysis of variance indicated several significant differences among the seven commercial preparations with respect to Cmax, Tmax, and AUC for sulfadiazine, sulfamerazine, and sulfamethazine. The in vitro behavior of each suspension was then studied by the paddle method of the Food and Drug Administration. A 0.5‐ml sample was introduced into 900ml of hydrochloric acid (2.2 × 10−‐4M) at 37° and dissolved using a paddle speed of 25rpm. Samples withdrawn at 15 and 30min were analyzed by high‐pressure liquid chromatography, and the percent of sulfadiazine, sulfamerazine, and sulfamethazine was calculated. Significant correlation was obtained between an in vivo parameter (Cmax for sulfadiazine) and an in vitro parameter (percent sulfadiazine dissolved in 30 min). Results indicate that this method is suitable for the in vitro screening of trisulfapyrimidine suspensions.