Take one 20 mg tablet each day.
You can take tamoxifen before or after meals.
The most common unwanted side-effects are hot flushes, and vaginal discharge and itchiness. There are also some less common but more serious side-effects - tell your doctor about any unusual vaginal bleeding, any pains in your leg or breathlessness, and any allergic-type reactions.
|Type of medicine||An anti-oestrogen (hormone receptor antagonist)|
|Used for||Breast cancer. Also used for fertility problems|
|Available as||Tablets and oral liquid medicine|
Treatment options for breast cancer include surgery, chemotherapy, radiotherapy and hormone treatment. Often a combination of two or more of these treatments is used. Tamoxifen is a hormone treatment.
Some breast cancers need the female hormone oestrogen to grow. The cells of these cancers have receptors on their surface that oestrogen can attach to and are called 'hormone receptor-positive' cancers. Tamoxifen works by blocking the receptors and this prevents oestrogen from reaching cancer cells, stopping them from growing.
Before taking tamoxifen
Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking tamoxifen it is important that your doctor or pharmacist knows:
- If you have unusual or irregular menstrual periods.
- If you have ever had a stroke, a blood clot in your lungs, or deep vein thrombosis (DVT).
- If you are pregnant or breastfeeding.
- If you have porphyria, a rare inherited blood disorder.
- If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines. It is also particularly important that you tell your doctor if you are taking a hormonal contraceptive ('the pill' or 'mini-pill') or hormone replacement therapy (HRT).
- If you have ever had an allergic reaction to a medicine.
How to take tamoxifen
- Before starting this treatment, read the manufacturer's printed information leaflet from inside the pack. The leaflet will give you more information about tamoxifen and a full list of side-effects which you may experience from taking it.
- Take one 20 mg tablet of tamoxifen each day, exactly as your doctor tells you to. Your dose will also be on the label of the pack to remind you.
- You may take tamoxifen at whatever time of day you find easiest to remember, but try to take your doses at the same time each day. This will help you avoid missing any doses. You can take tamoxifen before, during or after meals.
- If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose. Do not take two doses together to make up for a forgotten dose.
Getting the most from your treatment
- Try to keep your regular appointments with your doctor or clinic. This is so your doctor can check on your progress. You may need to have a blood test from time to time.
- If you are having an operation, tell the person carrying out the treatment that you are taking tamoxifen. This is because you may need to stop taking tamoxifen for a while before the operation.
- You must not get pregnant whilst you are on tamoxifen. Make sure you have discussed with your doctor which types of contraception are suitable for you and your partner, if this is relevant for you.
- If you buy any medicines, check with a pharmacist that they are suitable to take with your other medicines.
Can tamoxifen cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.
|Common tamoxifen side-effects||What can I do if I experience this?|
|Hot flushes||Try to keep cool by wearing light, airy clothes|
|Feeling sick (nausea) or being sick (vomiting)||Stick to simple foods and avoid rich or spicy foods|
|Headache||Drink plenty of water and ask a pharmacist to recommend a suitable painkiller. If the headaches continue, let your doctor know|
|Feeling light-headed or dizzy||If this happens, do not drive and do not use tools or machines until you feel better|
|Genital itching, menstrual changes, tumour pain||If any of these becomes troublesome, speak with your doctor|
Important: your doctor will have discussed with you the possibility of less common side-effects. You must let your doctor know straightaway if you develop any of the following:
- Pain or swelling in your lower leg, or any sudden breathlessness. Taking tamoxifen can increase the risk of you developing a blood clot in a leg vein (also known as a DVT), or in your lungs (also known as pulmonary embolism, or PE).
- Any swelling of your face or throat, breathing difficulties, or a severe rash. These may be signs of an allergic-type reaction.
- Irregular or unusual vaginal bleeding or discharge, or pain in your lower tummy (abdomen). Your doctor will want to check to see if there are any changes in the lining of your womb that could cause concern.
If you experience any other symptoms which you think may be due to this medicine, discuss them with your doctor or pharmacist.
How to store tamoxifen
- Keep all medicines out of the reach and sight of children.
- Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Further reading and references
Manufacturer's PIL, Tamoxifen 20 mg Tablets; Mylan, The electronic Medicines Compendium. Dated July 2018.
British National Formulary, 77th Edition (Mar 2019); British Medical Association and Royal Pharmaceutical Society of Great Britain, London.