Abstract
The mechanism of the intestinal transport of sulfonamides and the effect of chlorpromazine (CPZ) on it were studied using rat everted intestine in vitro. Sulfamethoxazole (SMZ) was accumulated in the serosal solution in the everted sac obeying the pH partition theory, while sulfisoxazole (SIX) was not accumulated despite the presence of the pH difference between the serosal and mucosal solutions. The reason was suggested that the microclimate pH on the mucosal surface of the intestine so decreased the amount of the unionized molecules of SIX that the transport rate of SIX was decreased to show no accumulation in the serosal solution within the sampling period. CPZ as well as metabolic inhibitors blocked the SMZ accumulation by inhibiting the growth of the pH difference. This effect was caused by the inhibition of the serosal alkalinization.
