Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy.

Objective: Grapefruit seed extract (GSE) is promoted as a natural product with antibacterial and antiviral properties. The aim of this study was to investigate the composition of some commercially available GSE products and evaluate their effect in vitro on two cytochrome P450 enzymes, CYP2C9 and CYP3A4.

Methods: A couple on lifelong treatment with warfarin and continuous regular follow-ups took some drops of a GSE product for 3 days.

Effects of herbal medicinal products and food supplements on induction of CYP1A2, CYP3A4 and MDR1 in the human colon carcinoma cell line LS180.

A selection of popular herbal medicinal products and food supplements were analysed for their potential to modulate the expression of the cytochrome P450 enzymes CYP1A2 and CYP3A4 and the transporter protein MDR1. A total of 31 products were analysed. Nine of the products have been approved by the Medical Products Agency (MPA) in Sweden and are marketed as herbal medicinal products.