Interaction between traditional Chinese medicine and Western medicine in rats--In-Chen-How and acetaminophen.

The purpose of this study is to evaluate the interaction effects of In-Chen-How (Artemisia capillaries Thunb.) on the pharmacokinetics of acetaminophen and on liver microsomal cytochrome P450 enzyme activity in rats. The rats were divided into control group (n = 8) without In-Chen-How and the pretreated group (n = 8) administered with In-Chen-How (approximately 1.0 mL x kg(-1), according to weight) for 5 consecutive days. Rats in the control group received water simultaneously. Each rat was then given acetaminophen. The pharmacokinetic parameters of acetaminophen of the two groups were significantly different. In the In-Chen-How pretreated group, the maximum concentration of acetaminophen and the area under the plasma concentration-time curve were reduced about 58.4%, 56.7% and 55.4%. To further explain the results, liver microsomal suspensions were obtained from rats that were randomly divided into control and In-Chen-How pretreated group. The levels of CYP1A2 and CYP2E1 in hepatic microsomal protein from pretreated group were increased as compared to that from the control group. It indicated that In-Chen-How can stimulate the activity of CYP isozymes. The changes in the pharmacokinetics of acetaminophen resulting from the administration of In-Chen-How are related to an increase in metabolic activity of CYP1A2 and CYP2E1.