Medication · hrt progesterone

Supplements and Norethisterone.

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

Norethisterone, sold under the brand names Utovlan, Elleste-Duet, Evorel-Conti, Noriday, is hormone replacement therapy (progesterone component).

Norethisterone is hormone replacement therapy (the progesterone component). It is prescribed alongside oestrogen in women with an intact uterus, to oppose endometrial hyperplasia driven by oestrogen. Micronised progesterone (Utrogestan) has replaced earlier synthetic progestogens in much of UK practice, given the better metabolic and breast cancer risk profile. Mechanism is GABA-A receptor modulation in addition to progesterone receptor activity. That is why bedtime dosing is standard; the sedating effect is useful. The supplement surface is small. Progesterone is metabolised by CYP3A4 but the dose is much lower than the oestrogen counterpart. The clinical signal from supplement interactions is correspondingly quieter. Symptom relief supplements (black cohosh, ashwagandha for sleep, magnesium glycinate for waking in the night) sit on top of HRT without strong interaction signals. The clinically important point is differentiating HRT progesterone use from progestogen as a contraceptive. Different agents, different goals, different dosing.

Below are the 2 documented pairs we have explicitly assessed against Norethisterone 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 speed up the breakdown of norethisterone, lowering its level in your blood. In an HRT or period-control setting this can mean breakthrough bleeding and reduced effect, and where norethisterone is providing contraceptive cover that cover can become unreliable. We treat this as a do-not-combine pair without specialist sign-off.

PMID 14663455 · PMID 13129991 · PMID 27444983 · BNF: Hypericum · BNF: Norethisterone

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

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. Norethisterone is a progestogen used in HRT and to control periods, so in theory vitex could pull against the hormone balance it is providing, and the medication could equally blunt what vitex is meant to do. There is no study showing this actually happens, so it is a caution rather than a firm warning. It is worth mentioning vitex to your prescriber before adding it.

PMID 7890021 · PMID 14974442 · PMID 18204102 · PMID 39519010 · BNF: Norethisterone

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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