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Selective oestrogen receptor modulator (SERM)

Tamoxifen

Brand names: Soltamox, Nolvadex

Adult dose

Dose: Breast cancer: 20mg PO OD x5–10 years. Anovulatory infertility: 20mg/day days 2-5 of cycle
Route: PO
Frequency: OD

Clinical pearls

  • ER-positive breast cancer (any stage), prevention in high-risk women
  • Counsel re abnormal vaginal bleeding (endometrial Ca)

Contraindications

  • Pregnancy
  • Concurrent strong CYP2D6 inhibitors (e.g. paroxetine, fluoxetine — avoid)
  • VTE history (relative)
  • Endometrial hyperplasia

Side effects

  • Hot flushes
  • VTE
  • Endometrial cancer
  • Stroke
  • Cataracts
  • Hepatotoxicity
  • Hypercalcaemia

Interactions

  • Strong CYP2D6 inhibitors (reduce active metabolite)
  • Warfarin (raised INR)
  • Anastrozole (avoid combination)

Monitoring

  • Endometrial symptoms
  • FBC
  • LFTs
  • Vision

Reference: BNF; NICE NG101; https://bnf.nice.org.uk/drugs/tamoxifen/. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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