Abstract
The effect of diphenhydramine on the intestinal absorption of sulfisomidine was investigated in rabbits. Diphenhydramine significantly reduced the mean blood sulfisomidine concentrations at 0.5 and 1.0 hours. In addition, diphenhydramine altered the maximum blood concentration (Cmax) and the time taken to reach the maximum blood concentration (Tmax) of sulfisomidine from 103.6±3.2 to 87.2±7.5μg/ml and from 1.1±0.2 to 2.1±0.5 hour, respectively. However, diphenhydramine was found to have little effect on the area under the blood concentration-time curve (AUCo-∝) or on the elimination half-life (t1/2) of sulfisomidine. Diphenhydramine also increased the amount of phenol-red remaining in the rabbit stomach from 26.8±4.1 to 46.5±4.5%. These results indicate that diphenhydramine decreases the rate but not the extent of sulfisomidine absorption by delaying the gastric emptying.
