BMA Concise Guide to Medicine & Drugs

Tamoxifen

Brand name Soltamox

Used in the following combined preparations None

QUICK REFERENCE

Drug group Anticancer drug

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Tamoxifen is an anti-oestrogen drug (oestrogen is a naturally occurring female sex hormone). It is used for two conditions: infertility and breast cancer. When given as treatment of certain types of infertility, the drug is taken only on certain days of the menstrual cycle. Used as an anticancer drug for breast cancer, tamoxifen works by blocking the effect of natural oestrogens that stimulate the growth of tumours with oestrogen receptors (oestrogen-receptor-positive tumours). This reduces the risk of tumours recurring after surgical removal of the tumour.

As its effect is specific, tamoxifen has fewer adverse effects than most other drugs used for breast cancer. However, it may cause eye damage if high doses are taken for long periods.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, liquid.

Frequency and timing of doses 1–2 x daily.

Adult dosage range 20mg daily (breast cancer). 20–80mg daily (infertility).

Onset of effect Side effects may be felt within days, but beneficial effects may take 4–10 weeks.

Duration of action Effects may be felt for several weeks after stopping the drug.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Do not stop the drug without consulting your doctor; stopping the drug may lead to worsening of your underlying condition.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.

POSSIBLE ADVERSE EFFECTS

Adverse effects of tamoxifen are rarely serious and do not usually necessitate treatment being stopped. Nausea, vomiting, hot flushes, and hair loss are the most common reactions; discuss with your doctor if these are severe. There is a small risk of endometrial cancer developing, so you should notify your doctor as soon as possible of any symptoms such as irregular vaginal bleeding or discharge. Rarely, bone and tumour pain, rash, itching, or blurred or reduced vision may occur; if so, consult your doctor. If you experience calf pain or swelling, contact your doctor immediately. Long-term use of the drug may cause other adverse effects (see Prolonged use).

INTERACTIONS

Anticoagulants People treated with anticoagulants such as warfarin usually need a lower dose of the anticoagulant.

SSRI antidepressants These may reduce the effectiveness of tamoxifen.

Anticancer medicines Cytotoxic medicines taken with tamoxifen may increase the risk of side effects, especially the risk of venous thrombosis.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You are pregnant or are planning a pregnancy.

· You have cataracts or poor eyesight.

· You suffer from porphyria.

· You have a history of venous thrombosis.

· You are taking other medicines.

Pregnancy Not usually prescribed. May have effects on the developing baby. Discuss with your doctor.

Breast-feeding Not usually prescribed. Discuss with your doctor.

Infants and children Not prescribed.

Over 60 No special problems.

Driving and hazardous work Do not drive until you have learned how tamoxifen affects you because the drug can cause dizziness and blurred vision.

Alcohol No known problems.

Surgery and general anaesthetics Tell your doctor or anaesthetist that you are taking tamoxifen before you have any surgery. You may be advised to stop taking it 6 weeks before.

PROLONGED USE

There is a risk of damage to the eye with long-term, high-dose treatment. There is also a small increased risk of endometrial cancer and venous thrombosis with long-term tamoxifen treatment but these risks are outweighed by the benefit of preventing recurrence of breast cancer.

Monitoring Eyesight may be tested periodically.