Tamoxifen for breast cancer
Revu par Sid DajaniDernière mise à jour par Michael Stewart, MRPharmSLast updated 24 Aug 2022
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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.
At a glance
Tamoxifen is a medicine used to treat breast cancer and fertility problems.
It is an anti-oestrogen medicine, meaning it blocks the effect of oestrogen on cancer cells.
Take one 20 mg tablet daily, at the same time each day.
Do not get pregnant while taking tamoxifen and discuss contraception with your doctor.
You must inform your doctor straight away if you develop leg pain, breathlessness, or unusual vaginal bleeding.
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About tamoxifen
Type de médicament | An anti-oestrogen (hormone receptor antagonist) |
Utilisé pour | Breast cancer. Also used for fertility problems |
Disponible sous forme de | Comprimés et médicaments liquides oraux |
Treatment options for cancer du sein include surgery, la chimiothérapie, la radiothérapie 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
Retour au sommaireSome 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).
Si vous êtes enceinte ou si vous allaitez.
Si vous avez la porphyrie, une maladie sanguine héréditaire rare.
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).
Si vous avez déjà eu une réaction allergique à un médicament.
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How to take tamoxifen
Retour au sommaireBefore 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.
Si vous oubliez de prendre une dose, prenez-la dès que vous vous en souvenez. Si vous ne vous en souvenez que le lendemain, sautez la dose oubliée. Ne prenez pas deux doses ensemble pour compenser une dose oubliée.
Tirer le meilleur parti de votre traitement
Retour au sommaireTry 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.
Si vous achetez des médicaments, vérifiez avec un pharmacien qu'ils sont compatibles avec vos autres médicaments.
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Can tamoxifen cause problems?
Retour au sommaireEn plus de leurs effets bénéfiques, la plupart des médicaments peuvent provoquer des effets secondaires indésirables, bien que tout le monde ne les ressente pas. Ceux-ci s'améliorent généralement à mesure que votre corps s'adapte au nouveau médicament, mais parlez à votre médecin ou à votre pharmacien si l'un des effets secondaires suivants persiste ou devient gênant.
Common tamoxifen side-effects | Que puis-je faire si je ressens cela ? |
Bouffées de chaleur | Try to keep cool by wearing light, airy clothes |
Se sentir malade (nausée) ou être malade (vomissements) | Stick to simple foods and avoid rich or spicy foods |
Maux de tête | Buvez beaucoup d'eau et demandez à un pharmacien de vous recommander un antidouleur approprié. Si les maux de tête persistent, informez votre médecin |
Se sentir étourdi ou avoir des vertiges | 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 immédiatement 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
Retour au sommaireGardez tous les médicaments hors de la portée et de la vue des enfants.
Conserver dans un endroit frais et sec, à l'abri de la chaleur et de la lumière directes.
Informations importantes sur tous les médicaments
Retour au sommaireInformations importantes sur tous les médicaments
Ne prenez jamais plus que la dose prescrite. Si vous soupçonnez que vous ou quelqu'un d'autre avez pris une surdose de ce médicament, rendez-vous au service des urgences de votre hôpital local. Emportez le contenant avec vous, même s'il est vide.
Ce médicament est pour vous. Ne le donnez jamais à d'autres personnes, même si leur état semble être le même que le vôtre.
Ne gardez pas de médicaments périmés ou indésirables. Apportez-les à votre pharmacie locale qui s'en débarrassera pour vous.
Si vous avez des questions concernant ce médicament, demandez à votre pharmacien.
Signaler les effets secondaires d'un médicament ou d'un vaccin
Si vous ressentez des effets secondaires, vous pouvez les signaler en ligne via le Yellow Card website.

Vous n'êtes pas sûr de mélanger des médicaments ?
Vérifiez les interactions possibles entre les médicaments, les compléments et les aliments avant de les prendre ensemble.
Questions fréquemment posées
What kind of conditions is tamoxifen used for, besides breast cancer?
Tamoxifen is primarily used for breast cancer, specifically hormone receptor-positive types. However, it can also be used to treat fertility problems.
How exactly does tamoxifen prevent breast cancer from growing?
Some breast cancers need oestrogen to grow. Tamoxifen works by blocking the receptors on the cancer cells that oestrogen would normally attach to. By preventing oestrogen from reaching these cells, it stops them from growing.
Are there any specific situations where I need to be extra careful or inform my doctor before taking tamoxifen?
Yes, it's important to tell your doctor or pharmacist if you've ever had a stroke, a blood clot in your lungs, or deep vein thrombosis (DVT). You should also mention if you have unusual menstrual periods, are pregnant or breastfeeding, have porphyria, or have had an allergic reaction to any medicine. Additionally, discuss any other medicines you are taking, especially hormonal contraceptives or hormone replacement therapy (HRT).
What should I do if I forget to take my daily dose of tamoxifen?
If you forget a dose, take it as soon as you remember. However, if you don't remember until the next day, you should skip the missed dose. Do not take two doses together to catch up for a forgotten dose.
Can I continue to use my usual contraceptive pill while taking tamoxifen?
It is particularly important to tell your doctor if you are taking a hormonal contraceptive, such as 'the pill' or 'mini-pill'. You must not get pregnant while on tamoxifen, so you should discuss suitable contraception options with your doctor.
What are some of the common side effects of tamoxifen and how can I manage them?
Common side effects include hot flushes (try to wear light, airy clothes), feeling sick or being sick (stick to simple foods), headaches (drink water, ask a pharmacist for pain relief), and feeling light-headed or dizzy (do not drive or use tools/machines until you feel better). If any side effects become troublesome or continue, speak to your doctor or pharmacist. Genital itching, menstrual changes, or tumour pain should also be discussed with your doctor if they become troublesome.
Are there any serious side effects of tamoxifen that I should be immediately concerned about?
Yes, you must let your doctor know straight away if you develop pain or swelling in your lower leg, or sudden breathlessness, as these could be signs of a blood clot. Also, severe allergic-type reactions such as swelling of your face or throat, breathing difficulties, or a severe rash require immediate medical attention. Irregular or unusual vaginal bleeding or discharge, or pain in your lower tummy, also needs to be checked by your doctor promptly due to potential changes in the womb lining.
Lectures complémentaires et références
- Manufacturer's PIL, Tamoxifen 20 mg Tablets; Mylan, The electronic Medicines Compendium. Dated May 2021.
- Médicaments Complets BNF 89e Édition; Association Médicale Britannique et Société Royale Pharmaceutique de Grande-Bretagne, Londres.
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About the authorView full bio

Michael Stewart, MRPharmS
Medicine Leaflet Review Manager – Contractor, Pharmacist
BPharm (Hons), MRPharmS
Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.
About the reviewer

Sid Dajani
Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.
Historique de l'article
Les informations sur cette page sont rédigées et examinées par des cliniciens qualifiés.
Next review due: 22 Feb 2027
24 Aug 2022 | Dernière version

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