Primary Research · 2003
Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trial
Evans et al. · Anaesthesia, 2003
Key finding
Breakthrough bleeding incidence: control 6/17 (35%), cycle A (SJW BID) 13/17 (77%, p<0.015), cycle B (SJW TID) 15/17 (88%, p<0.001). Dose-response evident. No ovulation detected during SJW combination (progesterone remained suppressed), but follicle-like structures observed sporadically. Authors conclude SJW should be used with caution in women on OCs due to bleeding and reduced progestin levels potentially elevating pregnancy risk.
Read the paper
Open sourcehttps://pmc.ncbi.nlm.nih.gov/articles/PMC1884294/
About this page
Formulate maintains a registry of clinical studies cited across its guides and evidence grades. This page links the study metadata to the content that cites it — one canonical entry per landmark study.
The full citation chain is public so readers can verify claims without hunting through individual guide pages. Browse all cited studies →
Note: Study summaries on this page are editorial interpretations of the research. Always consult the primary source before drawing clinical conclusions.