The effect of St John’s wort extracts on CYP3A: a systematic review of prospective clinical trials

• Published in: British journal of clinical pharmacology 2006-11, Vol.62 (5), p.512-526
• Main Authors: Whitten, D. L., Myers, S. P., Hawrelak, J. A., Wohlmuth, H.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Biological and medical sciences; Clinical Trials as Topic; CYP3A; Cytochrome P-450 CYP3A - metabolism; cytochrome P450; Female; Herb-Drug Interactions; Humans; Hypericum - metabolism; Hypericum perforatum; Male; Medical sciences; Middle Aged; Pharmacology. Drug treatments; Plant Extracts - metabolism; Plant Extracts - pharmacology; Prospective Studies; St John’s wort; Systematic Review
• ISSN: 0306-5251; 1365-2125
• DOI: 10.1111/j.1365-2125.2006.02755.x

Aim The aim of this systematic review was to assess the quality and outcomes of clinical trials investigating the effect of St John’s wort extracts on the metabolism of drugs by CYP3A. Methods Prospective clinical trials assessing the effect of St John’s wort (SJW) extracts on metabolism by CYP3A were identified through computer‐based searches (from their inception to May 2005) of Medline, Cinahl, PsycINFO, AMED, Current Contents and Embase, hand‐searches of bibliographies of relevant papers and consultation with manufacturers and researchers in the field. Two reviewers selected trials for inclusion, independently extracted data and recorded details on study design. Results Thirty‐one studies met the eligibility criteria. More than two‐thirds of the studies employed a before‐and‐after design, less than one‐third of the studies used a crossover design, and only three studies were double‐blind and placebo controlled. In 12 studies the SJW extract had been assayed, and 14 studies stated the specific SJW extract used. Results from 26 studies, including all of the 19 studies that used high‐dose hyperforin extracts (>10 mg day−1), had outcomes consistent with CYP3A induction. The three studies using low‐dose hyperforin extracts (