Absorption of morphine, butylscopolamine, mecamylamine and phenobarbitone from the small intestine of the triparanol-treated rat in situ.

The absorption of three basic drugs (morphine, butylscopolamine and mecamylamine) and an acidic drug (phenobarbitone) from the rat small intestine in situ was investigated by using a single perfusion technique. The effect of intestinal damage on absorption was studied by treating rats with triparanol 25-50 mg/kg every 24 h for three weeks. Treatment with triparanol decreased the cholesterol concentration in the intestinal wall. The absorption of morphine and mecamylamine was increased by treatment with triparanol, whereas the absorption of butylscopolamine was decreased and that of phenobarbitone remained unaltered. Treatment with triparanol decreased the concentration of mecamylamine in the intestinal wall, but the concentrations of other drugs were unchanged. When comparing the present in situ and previous in vitro results the decreased absorption of butylscopolamine after triparanol in situ was opposite to the finding in vitro. The increased absorption of morphine and unaltered absorption of phenobarbitone were in accordance with the finding in vitro. In situ the absorption of mecamylamine was increased, although in vitro it was unchanged. The structural damage, differences in composition of the intestinal wall and intestinal blood flow are supposed to be the reasons for changes in absorption.