Inhibition of human cytochrome p450 metabolism by blended herbal products and vitamins.

Purpose: The use of supplements as herbal and micronutrient natural health products with conventional health products has become increasingly popular. It has been reported that some herbal products can inhibit the activity of cytochrome P450-mediated metabolism and drug disposition. This study was designed to investigate a case report of a severe adverse event to determine the potential interactions of femMED, Thyrosense and vitamins on cytochrome P450-mediated drug metabolism.

Modulation of human cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) in Caco-2 cell monolayers by selected commercial-source milk thistle and goldenseal products.

In this study, we used an in vitro Caco-2 cell monolayer model to evaluate aqueous extracts of commercial-source goldenseal (Hydrastis canadensis) and milk thistle (Silybum marianum) capsule formulations, their marker phytochemicals (berberine and silibinin, respectively), as well as dillapiol, vinblastine, and the HIV protease inhibitor saquinavir for their ability to modulate CYP3A4 and ABCB1 expression after short-term exposure (48 h). Both upregulation and downregulation of CYP3A4 expression was observed with extracts of varying concentrations of the two natural health products (NHPs). CYP3A4 was highly responsive in our system, showing a strong dose-dependent modulation by the CYP3A4 inhibitor dillapiol (upregulation) and the milk thistle flavonolignan silibinin (downregulation).

In vitro activity of commercial valerian root extracts against human cytochrome P450 3A4.

Purpose: Valerian root ( Valeriana officinalis L.) has been used since antiquity as a medicinal herb. Recent studies have found that certain herbal products used concomitantly with conventional therapeutic products can markedly affect drug disposition.