Asked on Healicus
Can you take St John's wort with the pill?
Answer published by a reader on . AI-generated from the sources below; general educational information, not medical advice.
No — St. John's wort significantly reduces how well the contraceptive pill works, and this is a well-documented, clinically serious interaction.
A randomised trial in women taking a low-dose combined pill found that adding St. John's wort increased breakthrough bleeding and reduced blood levels of both ethinyloestradiol and the progestogen component — signs that the pill was being cleared from the body faster than normal 1Pfrunder A et al., Br J Clin Pharmacol, 2003 — Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trialRandomised trial · Br J Clin Pharmacol 2003There was no evidence of ovulation during low-dose oral contraceptive and St John's wort extract combination therapy, but intracyclic bleeding episodes increased.Open on pubmed.ncbi.nlm.nih.gov ↗. The mechanism is well understood: hyperforin in the extract switches on liver enzymes (CYP3A4, CYP2C9, CYP1A2) and a drug transporter called P-glycoprotein, which together speed up the breakdown of many medicines 2Henderson L et al., Br J Clin Pharmacol, 2002 — St John's wort (Hypericum perforatum): drug interactions and clinical outcomesSystematic review · Br J Clin Pharmacol 2002In Sweden and the UK the potential risks to patients were judged to be significant and therefore information about the interactions was provided to health care professionals and patients.Open on pubmed.ncbi.nlm.nih.gov ↗. Oral contraceptives are squarely on that list, alongside warfarin, ciclosporin, HIV protease inhibitors, digoxin, and others 2Henderson L et al., Br J Clin Pharmacol, 2002 — St John's wort (Hypericum perforatum): drug interactions and clinical outcomesSystematic review · Br J Clin Pharmacol 2002In Sweden and the UK the potential risks to patients were judged to be significant and therefore information about the interactions was provided to health care professionals and patients.Open on pubmed.ncbi.nlm.nih.gov ↗.
The practical upshot: taking both together raises the real risk of contraceptive failure — unwanted pregnancies have been reported in this combination 1Pfrunder A et al., Br J Clin Pharmacol, 2003 — Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trialRandomised trial · Br J Clin Pharmacol 2003There was no evidence of ovulation during low-dose oral contraceptive and St John's wort extract combination therapy, but intracyclic bleeding episodes increased.Open on pubmed.ncbi.nlm.nih.gov ↗. NICE advises against St. John's wort entirely in people on interacting medications, and this is one of the clearest examples of why.
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Have a follow-up, or a question of your own? Every answer cites Cochrane, EU regulators, guideline bodies or trials in leading journals.