Effect of Several Chinese Natural Health Products of Human Cytochrome P450 Metabolism.

PURPOSE: Traditional Chinese medicines (TCM) are believed by many to be safe and used for self-medication without supervision. Although the risk appears to be low, certain TCM have been associated with a number of serious adverse reactions. A preliminary study was undertaken with 12 products using a human cytochrome P450 (CYP450) isozyme assay to determine if these products could affect human drug metabolism. METHODS: Aliquots of samples were analyzed directly or as extracts for their potential to affect CYP450 2C9, 2C19, 2D6, and 3A4 mediated-metabolism of marker substrates using an in vitro fluorometric microtiter plate assay. RESULTS: One product was found to be a Chinese Proprietary Medicine (CPM). Most aqueous extracts inhibited CYP450 mediated-metabolism of at least 3 isozymes (ranging from 25-100%). All liquid samples markedly inhibited the metabolism of all 4 isozymes. De le ke chuan kang and Rensheng dao were the strongest CYP450 inhibitors. CONCLUSIONS: Our in vitro findings demonstrate that TCM can inhibit CYP450 2C9, 2C19, 2D6 and 3A4 mediated-metabolism. TCM need to be examined further under clinical settings to determine if potential interactions will occur that affect the safety and efficacy of conventional therapeutic products.