Abstract
The effect of complex formation on drug absorption from rat small intestine by recirculating perfusion method has been studied by following systems : sodium p-aminosalicylate (NaPAS)-sulfisoxazole, NaPAS-sulfisomidine, NaPAS-sulfamethoxypyridazine, sodium salicylate-caffeine, hydroxyethyltheophylline-nicotinamide, and its reverse combination, and the absorption rate of the latter of the each combinations was measured in the presence of the former. It was found that the absorption rate of each drug could be modified by the complex formation. Results of these studies were correlated with kinetic analysis based on the absorption rate constant in the absence and in the presence of complexing agent, and the equilibrium constant. It appears under the experimental conditions and used combinations of drugs that the complex itself may be absorbed, and that its absorption rate is slower than that of free drug. Complexation of the drug with complexing one decreased the apparent partition coefficient of the former. This suggests one possible mechanism for the absorption of complex.
