Medication · combined oral contraceptive

Supplements and Ethinylestradiol with desogestrel.

Every documented pair, every citation. Below: 2 documented pairs grouped by mechanism.

Ethinylestradiol with desogestrel, sold under the brand names Marvelon, Mercilon, Gedarel, is a combined oral contraceptive: it provides oestrogen and progestogen for ovulation suppression and cycle control.

Ethinylestradiol with desogestrel is a combined oral contraceptive, providing oestrogen and progestogen for ovulation suppression and cycle control. The class is metabolised by CYP3A4 in the liver. That is where the supplement surface sits. St John's Wort induces CYP3A4 strongly enough to reduce contraceptive efficacy. The BNF and MHRA both flag this, and the Faculty of Sexual and Reproductive Healthcare advises against the combination. Several other strong CYP3A4 inducers (rifampicin, certain antiepileptics) carry the same concern. Among supplements at standard doses the signal is much smaller, but at high doses some 3A4-active compounds may have a marginal effect. The other clinically important issue is the venous thromboembolism risk profile. Third-generation progestogens carry a slightly higher VTE signal than second-generation. Any supplement decision in a patient at high VTE risk (smoker, obesity, family history) should account for the baseline.

Below are the 2 documented pairs we have explicitly assessed against Ethinylestradiol with desogestrel in the Distil database: 1 red and 1 amber. The pairs cluster around 2 mechanisms: CYP3A4 induction and Hormonal axis modulation. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.

Documented interactions

CYP3A4 induction

Red St John's Wort

St John's Wort can reduce the contraceptive reliability of the combined pill. Breakthrough bleeding is the warning sign, and unintended pregnancies have been reported on this combination. We treat this as a do-not-combine pair.

PMID 14616430 · PMID 27444983 · BNF: Hypericum

Hormonal axis modulation

Amber Vitex

Vitex (chasteberry) acts on the body's hormone signals: it lowers prolactin and, in lab studies, gently nudges oestrogen and progesterone receptors. The combined pill works by holding your hormones at set levels, so in theory vitex could work against that balance, and the pill's hormones could equally blunt what vitex is meant to do. There is no study showing the pill actually fails when vitex is added, so this is a caution rather than a firm warning. If you take the combined pill, mention vitex to your prescriber before adding it, and treat any breakthrough bleeding as a reason to check in.

PMID 7890021 · PMID 14974442 · PMID 18204102 · PMID 39519010 · BNF: Ethinylestradiol-with-desogestrel

Reviewer-flagged: awaiting clinical-reviewer sign-off.

What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.

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For adults over 18. This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.

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