Differences in the effects of piperine and piperonyl butoxide on hepatic drug-metabolizing enzyme system in rats.

An i.p. administration of rats with piperine (100 mg/kg) and piperonyl butoxide (400 mg/kg) produced a significant decrease in hepatic cytochrome P-450, and activities of benzphetamine N-demethylase, aminopyrine N-demethylase and aniline hydroxylase 1 hr after the treatment. Twenty-four hr later, these parameters along with cytochrome b5 and NADPH-cytochrome c reductase remained depressed only in piperine-treated rats. In contrast, piperonyl butoxide caused a significant induction of these parameters with the exception of cytochrome b5 and aminopyrine N-demethylase, which were up by 36 and 33% over their respective controls but not significantly. These results point up that effect of piperine on hepatic mixed-function oxidases is monophasic while that of piperonyl butoxide is biphasic.