Tamoxifen is used to treat breast cancer. It also lowers the chance of getting breast cancer in women who are at high risk of acquiring the disease.
This medicine can also be used to treat infertility in women caused by a failure to properly produce and release eggs (a process known as ovulation).
Tamoxifen may be used to treat other conditions as decided by your doctor.
Take Tamoxifen exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.
You may take this medicine with or without food. Try to take it at the same time each day.
Tamoxifen is available as a tablet or oral solution.
If you are taking an oral solution, shake the bottle well before you take it to ensure that the liquid is evenly mixed. Use the measuring spoon or cup provided to measure out your prescribed dose.
If you are taking Tamoxifen to lower your chances of having breast cancer, it may be necessary for you to take this medicine for a long time, such as for a few years. Your doctor will advise you on the treatment timeframe.
Tamoxifen must be taken regularly for it to be effective. Continue taking this medicine even when you feel better. Do not stop taking it unless instructed by the doctor.
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.
DO NOT double a dose under any circumstances.
If you often forget to take your medicine, let your doctor and pharmacist know.
If you are taking this medicine to treat infertility or lower your chances of having breast cancer, alert your doctor if you have the following conditions:
- with or a history of deep vein thrombosis (blood clot in the leg veins)
- with or a history of pulmonary embolism (blood clot in the lung artery)
as Tamoxifen may not be suitable for you.
Do not take this medicine if you are pregnant or planning to have a baby soon. If you become pregnant while being treated or within 2 months after stopping the treatment with Tamoxifen, alert your doctor immediately. This medicine may cause harm to your unborn child. Birth control medicines containing hormones may not be effective. You may wish to discuss other reliable methods of birth control with your doctor.
Do not breastfeed while you are being treated with this medicine.
Do not take Tamoxifen if you are taking anastrozole (other medicine for breast cancer).
If you are taking this medicine to lower your chances of having breast cancer, do not take it with blood-thinning medicines such as warfarin.
Inform your doctor if you have the following conditions:
- family history of stroke or blood clotting disorders
- conditions which increase the risk of blood clots e.g. obesity, smoking, prolonged immobility
If you are going to have certain laboratory tests (e.g. thyroid test, Pap smear) or an operation, including minor surgery and dental work, inform your doctor or dentist that you are taking this medicine.
Certain genetic traits can affect the effectiveness of Tamoxifen. Individuals who are poor or intermediate metabolisers of CYP2D6 may respond poorer to this medicine. Although not routinely done, your doctor may advise you to undergo genetic testing to check if Tamoxifen is best suited for you. If you know you have this gene type, inform your doctor.
Why is it important to keep my appointments with the doctor?
Keep your appointments with your doctor. Your doctor needs to monitor your condition and check your response to the medication regularly.
- Pregnancy tests must be done before treatment to know if this medicine is suited for you to take.
- Routine tests (e.g. complete blood count, liver function, cholesterol or electrolyte levels, breast or eye examination) may be done while you are being treated with Tamoxifen. Your doctor will advise you about how often you need to have these tests.
- Regular monitoring for signs of unusual vaginal bleeding, menstrual irregularities, and pain in the pelvic area (lower part of the abdomen between the hip bones) may also be needed.
Tamoxifen may cause light-headedness, tiredness, or some problems with your eyesight. If affected, do not drive or take part in any activity in which you need to be alert or need to see clearly.
Other side effects include any of the following: headache, nausea, vomiting, diarrhoea, constipation, changes in taste, muscle or joint pain, hot flushes, and hair loss.
Some side effects may need immediate medical help. Alert your doctor quickly if you experience any of the following:
- unusual vaginal bleeding, changes in vaginal discharge, menstrual irregularities, pain or pressure in the pelvic area
- pain, swelling and tenderness in your leg accompanied by redness and warmth; coughing up blood with shortness of breath and chest pain
- sudden weakness, numbness or tingling sensation in the face, hands or feet particularly on one side of the body; sudden confusion, difficulty speaking, dizziness, and loss of balance
- visual disturbances e.g. blurred vision, clouding of the lens of the eye
- yellowing of the skin or eyes, abdominal pain, dark coloured urine, swelling in the legs and ankles
- rashes, breathlessness, swollen eyes, mouth, face or throat
This medicine may cause the level of your red blood cells, white blood cells and platelets to drop.
Red blood cells carry oxygen around your body. A fall in the level of red blood cells may make you feel tired and worn out.
White blood cells help your body to fight infections. A fall in the level of your white blood cells may put you at higher risk for infections, such as coughs, colds and flu, which may lead to more serious infections. Avoid crowded places and people who are sick. Inform your doctor if you have a fever, or a cough or flu that does not go away.
Platelets help your blood to clot when there is a cut in the skin. A fall in the level of your platelets may put you at risk of bleeding more than usual. Do not take part in activities where you may fall or get injured, such as contact sports. Inform your doctor if you get any unusual bruising (large bruises or several bruises, especially if the bruises appeared on their own) or bleeding that takes a long time to stop (for example, too much bleeding when you floss or brush your teeth).
Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Do not take Tamoxifen if you are taking anastrozole (other medicine for breast cancer).
If you are taking this medicine to lower your chances of having breast cancer, do not take it with blood-thinning medicines such as warfarin.
Inform your doctor and pharmacist if you are taking any of these medicines:
- other medicines used to treat cancer e.g. aminoglutethimide, letrozole
- medicines to treat depression e.g. bupropion, fluoxetine, paroxetine
- rifampicin (medicine to treat tuberculosis or TB)
- quinidine (medicine for irregular heartbeat)
This list does not include all medicines that may interact with Tamoxifen.
Inform your doctor if you are currently taking hormonal birth control pills as this may reduce the effectiveness of this medicine. You should not stop or start any birth control pills without first informing your doctor. Ask your doctor about using non-hormonal birth control as an alternative while being treated with Tamoxifen.
Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements and medicines that you buy without a prescription.
Avoid alcohol.
Avoid excessive consumption (more than 1 litre a day) of grapefruit juice.
Store in a cool, dry place away from the reach of children. Protect from light.
Do not refrigerate or freeze the oral solution.
Medicines must not be used past the expiry date.
As this is a cancer medicine, always return any unused or expired tablets/solution to the clinic, hospital or pharmacy for disposal. Do not throw it away in the household waste.
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