title: Clinical assessment of CYP2D6-mediated herb-drug interactions in humans: effects of milk thistle, black cohosh, goldenseal, kava kava, St. John's wort, and Echinacea.
abstract: Cytochrome P450 2D6 (CYP2D6), an important CYP isoform with regard to drug-drug interactions, accounts for the metabolism of approximately 30% of all medications. To date, few studies have assessed the effects of botanical supplementation on human CYP2D6 activity in vivo. Six botanical extracts were evaluated in three separate studies (two extracts per study), each incorporating 16 healthy volunteers (eight females). Subjects were randomized to receive a standardized botanical extract for 14 days on separate occasions. A 30-day washout period was interposed between each supplementation phase. In study 1, subjects received milk thistle (Silybum marianum) and black cohosh (Cimicifuga racemosa). In study 2, kava kava (Piper methysticum) and goldenseal (Hydrastis canadensis) extracts were administered, and in study 3 subjects received St. John's wort (Hypericum perforatum) and Echinacea (Echinacea purpurea). The CYP2D6 substrate, debrisoquine (5 mg), was administered before and at the end of supplementation. Pre- and post-supplementation phenotypic trait measurements were determined for CYP2D6 using 8-h debrisoquine urinary recovery ratios (DURR). Comparisons of pre- and post-supplementation DURR revealed significant inhibition (approximately 50%) of CYP2D6 activity for goldenseal, but not for the other extracts. Accordingly, adverse herb-drug interactions may result with concomitant ingestion of goldenseal supplements and drugs that are CYP2D6 substrates.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. gurleybillyj@uams.edu
authors.forename: Bill J
authors.initials: BJ
authors.lastname: Gurley
authors.forename: Ashley
authors.initials: A
authors.lastname: Swain
authors.forename: Martha A
authors.initials: MA
authors.lastname: Hubbard
authors.forename: D Keith
authors.initials: DK
authors.lastname: Williams
authors.forename: Gary
authors.initials: G
authors.lastname: Barone
authors.forename: Faith
authors.initials: F
authors.lastname: Hartsfield
authors.forename: Yudong
authors.initials: Y
authors.lastname: Tong
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Carrier
authors.forename: Shreekar
authors.initials: S
authors.lastname: Cheboyina
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Battu
mesh_terms: D031885:Cimicifuga / Q000378:metabolism; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D019587:Dietary Supplements; D020900:Echinacea / Q000378:metabolism; D041743:Herb-Drug Interactions; D006801:Humans; D039321:Hydrastis / Q000009:adverse effects* / Q000378:metabolism; D020902:Hypericum / Q000378:metabolism; D020901:Kava / Q000378:metabolism; D020944:Silybum marianum / Q000378:metabolism; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology*
chemical_list: D010936:Plant Extracts; D019389:Cytochrome P-450 CYP2D6