TAMOXIFEN

Oestrogen-receptor antagonist

Dosage Forms

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Tablet

20 mg

Uses

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  • Adjuvant treatment of estrogen-receptor-positive breast cancer
  • Metastatic breast cancer
  • Anovulatory infertility

Dose and Duration

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Adjuvant in breast cancer treatment

Adult: 20 mg daily in 1–2 divided doses for 5 years.

Metastatic breast cancer

Adult: 20–40 mg daily in 1–2 divided doses.

Anovulatory infertility

Adult: 20 mg daily from day 2 to day 5 of the cycle, dose increased if necessary to 40 mg then 80 mg in subsequent cycles. If cycles are irregular, start initial course on any day with subsequent course 45 days later or on day 2 if menstruation occurs.

Contra-indications

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  • Pregnancy
  • Breast-feeding
  • Porphyria
  • Treatment of infertility if personal or family history of idiopathic venous thromboembolism or genetic pre-disposition to thromboembolism

Side Effects

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  • Hot flushes
  • Vaginal bleeding discharge, suppression of menstruation
  • Pruritus vulvae
  • Nausea
  • Headache, light-headedness
  • Tumour flare
  • Decreased platelet counts
  • Visual disturbances
  • Alopecia
  • Stevens-Johnson syndrome

Interactions

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  • Warfarin (enhanced anticoagulant effect)
  • Fluoxetine, paroxetine, droperidol (metabolism of tamoxifen to active metabolite possibly inhibited)

Patient Instructions

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  • Report sudden breathlessness or pain in the calf of one leg.

Pregnancy

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  • Do not use.

Breast-feeding

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  • Discontinue breastfeeding.

Storage

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  • Store below 25°C in original package to protect from light. Do not refrigerate or freeze.

⚠️ Caution

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  • Monitor endometrial changes due to an increased risk of hyperplasia, polyps, cancer and uterine sarcoma. Examine patients promptly if abnormal vaginal bleeding occurs.
  • Increased risk of thromboembolism particularly during and immediately after major surgery or periods of immobility. Risk is increased when tamoxifen is given together with antineoplastic drugs.
  • Use with caution in pre-menopausal women with cystic ovarian swellings.
  • Ensure appropriate contraception in women during treatment and for at least 2 months following treatment.
  • Tamoxifen suppresses lactation and should be avoided during breast-feeding unless potential benefits risk.
  • Anticancer medicines should only be handled by health workers trained and experienced in cytotoxic medicines.