Effect of short-chain fatty acids on the intestinal absorption of drugs in the rat.

Abstract

The effect of propionic, butyric, and caproic acid, and of methyl butyrate on the absorption of various water-soluble drugs from the rat small intestine were investigated using the in situ perfusion technique. In preliminary experiment, butyric acid was absorbed rapidly by an active-like transport system. Fatty acids inhibited the absorption of anionic drugs (sulfisoxazole, salicylic acid, etc.), but enhanced the absorption of neutral drugs (caffeine, sulfanilamide, etc.) and cationic drugs (metoclopramide, quinine, etc.) at pH 6.5. In contrast, methyl butyrate enhanced the absorption of drugs in any case. The enhancement of apparent water absorption was observed in the presence of fatty acids and methyl butyrate, and the pH of perfusate containing fatty acids rose slightly after experiments. Butyric acid enhanced the exsorption rate of sulfisoxazole, but inhibited that of metoclopramide. Possible mechanisms of these effects are discussed.