Medication · serm

Supplements and Tamoxifen.

Not yet catalogued in the Distil interactions database. We surface that distinction explicitly.

Tamoxifen, sold under the brand name Nolvadex, is a selective oestrogen receptor modulator (SERM).

Tamoxifen is a selective oestrogen receptor modulator (SERM). The class shows oestrogen agonist and antagonist effects that vary by tissue, which is what gives this group of drugs its distinctive clinical profile. Tamoxifen and raloxifene are the dominant UK agents. Tamoxifen is used in breast cancer that is positive for the oestrogen receptor. Raloxifene is used in osteoporosis after menopause. Mechanism varies by tissue. Agonist at bone, which gives the osteoporosis benefit. Antagonist at breast tissue, which gives the cancer benefit. Variable at endometrium and cardiovascular tissue, which underlies the differential VTE and endometrial cancer risk profiles. The supplement surface for tamoxifen centres on CYP2D6. Tamoxifen is a prodrug converted to endoxifen by CYP2D6. CYP2D6 inhibitors (some SSRIs particularly fluoxetine and paroxetine, certain supplements at high doses) reduce active metabolite formation. The clinical implication is real enough that oncologists generally avoid the CYP2D6 inhibiting SSRIs in tamoxifen patients. Supplements with phyto-oestrogenic activity (soya isoflavones, red clover) warrant care during active treatment.

We have not yet completed an explicit assessment of supplement interactions with Tamoxifen in the Distil database. That is different from saying nothing exists. We surface this distinction deliberately: the Distil checker tells you when we have explicitly assessed a pair and when we have not, because both are useful information. If you take Tamoxifen alongside a supplement, the checker below will surface anything already in our database, and the missing-item form at the bottom of the page routes uncatalogued pairs into our next curation pass.

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.

Your supplements

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Your medications

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How we decide

How we grade severity, choose what's in scope, and what we exclude.

Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.

Read the full methodology

Your whole stack

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This page checks the pairs you enter. The personalised Distil report goes further:

the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
where your current routine may be leaving you short of your goals
the evidence-backed compounds worth adding, and the ones worth dropping

It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.

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Something missing?

If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.

Thanks, that's logged. We go through flagged items every week.

Distil's interactions database is reviewed and updated every quarter. We grade evidence transparently and publish our methodology, including every database change, at /about/methodology. This tool is information, not a substitute for clinical judgement. If you take medication and supplements together, your GP or pharmacist can review your full regimen against your medical history. If you want a full personalised stack reasoned against this same database, the Distil report is the next step up.