An anomalous effect of the intermediate products of riboflavine photolysis on the intestinal absorption of poorly absorbed water-solbule drug in rats.

The influence of the intermediate products of riboflavine photolysis on the absorption of poorly absorbed water-soluble drugs from the rat small intestine has been examined using an in situ recirculation technique. The absorption of phenol red, bromphenol blue (BPB) and their biliary excretion, and lactose isonicotinoyl-hydrazone (lactose-INH) and its plasma concentration were increased in experiments made in the presence of light in contrast to other made in the dark. The absorption of both phenol red and lactose-INH were concentration-dependent. On the other hand, a saturation phenomenon was demonstrated when the concentration of phenol red was kept constant while that of the water-soluble compound flavine mononucleotide (FMN) was changed. The results which were obtained from pretreatment experiments suggest an alteration in the permeability of the intestinal membrane. No enhancement effect could be demonstrated for lumichrome in the presence of absence of light.