Tamoxifen

Sounds like 'ta-mox-e-fen'

Key points about tamoxifen

Tamoxifen is used to treat breast cancer.
Tamoxifen is a type of hormone therapy that slows the growth of cancer by blocking the effects of oestrogen.
Find out how to take it safely and possible side effects.

Tamoxifen belongs to a group of medicines known as non-steroidal anti-oestrogens and is used to treat some types of breast cancer. Some breast cancers need the hormone oestrogen to grow. These types of breast cancer are called oestrogen receptor-positive (ER-positive) breast cancers. Tamoxifen slows the growth of the cancer by blocking the effects of oestrogen in your breast.

Tamoxifen can be taken by women (whether or not they've been through menopause) and can also be taken by men who have breast cancer. Read more about breast cancer.

In New Zealand, tamoxifen is available as tablets (10 mg and 20 mg).

The usual dose of tamoxifen is 20 mg once a day.
Tamoxifen is a long-term treatment; you may have to take it for several years.
Always take your tamoxifen exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

Timing: Take tamoxifen at the same time each day, either in the morning or the evening.
You can take tamoxifen with or without food. If you have nausea (feeling sick), try taking tamoxifen with food or just before bed.
Missed dose: If you forget to take your dose, take it as soon as you remember. But if it's nearly time for your next dose, just take the next dose at the right time. Don't take double the dose.
Keep taking tamoxifen regularly. Do not stop taking tamoxifen suddenly; talk to your doctor before stopping.

Here are some things to know when you're taking tamoxifen. Other things may be important as well, so ask your healthcare provider what you should know about.

Increased risk of blood clots: Tamoxifen increases your risk of getting blood clots in your leg (deep vein thrombosis or DVT) or your lung (called pulmonary embolism). Blood clots can be harmful. If you have any of the following symptoms, get medical attention immediately:
- signs of blood clots in your leg, eg, pain, redness, heat and swelling of your calf, leg or thigh
- signs of a blood clot in your lung, eg, a sudden shortness of breath, tightness in your chest, an unexplained cough or if you cough up blood.

Travel: tell your doctor if you're planning long-distance plane, car or train travel. Long periods of sitting can increase your risk of blood clots. You may need to wear compression stockings (tight-fitting stockings that apply pressure to help blood flow). These need to be correctly fitted so get advice from a pharmacist or another healthcare provider.
Surgery: this increases your risk of blood clots. You may need to stop taking tamoxifen a few days before and after the surgery. Tell your doctor or dentist (for dental surgery) that you're taking tamoxifen.
Driving: Tamoxifen can make you drowsy, especially when you first start taking it. Avoid driving and doing other tasks where you need to be alert until you know how tamoxifen affects you. It's best to take it at bedtime if it makes you drowsy. Limit alcohol intake, this can make drowsiness worse.
Contraception: Tamoxifen blocks female hormones but is not a contraceptive. If you are able to become pregnant, discuss contraception with your healthcare provider.
Pregnancy: It's recommended to wait 9 months after stopping treatment before becoming pregnant. Tell your doctor immediately if you become pregnant while taking tamoxifen or within 9 months of stopping treatment.
Other medicines: Tamoxifen interacts with some medicines, herbal supplements and rongoā Māori, so check with your doctor or pharmacist before starting tamoxifen and before starting any new products.

Like all medicines, tamoxifen can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Hot flushes and sweats

These are common when you are taking tamoxifen. Hot flushes and sweats may improve after the first few months. You can try to reduce this effect by not smoking, reducing alcohol and avoiding hot drinks containing caffeine, eg, tea and coffee. Try to dress in layers, so you can remove clothes as needed, and wear clothes made from natural fabrics like cotton. If hot flushes are troubling you, tell your healthcare provider. There are medicines that can help reduce them..

Increased risk of blood clots

Taking tamoxifen increases your risk of getting blood clots in your leg (deep vein thrombosis or DVT) or your lung (called pulmonary embolism). Blood clots can be harmful. If you have any of the following symptoms, get medical attention immediately:

signs of blood clots in your leg, eg, pain, redness, heat and swelling of your calf, leg or thigh
signs of a blood clot in your lung, eg, a sudden shortness of breath, tightness in your chest, an unexplained cough or coughing up blood.

Other side effects

Side effects	What should I do?
Nausea (feeling sick) or vomiting	Try taking tamoxifen with food or just before bed. Tell your doctor if this bothers you. Don't drink alcohol, this will make your nausea worse.
Dizziness Feeling tired Light-headed	These may improve with time. Be careful when driving or using tools until you know how this medicine affects you. Tell your doctor if this bothers you. Don't drink alcohol, this will make these symptoms worse.
Headache Sleep problems Weight gain	These may improve with time. Tell your doctor if they bother you.
Heavy bleeding during your periods (heavier or more painful than usual), or unusual bleeding between your periods.	Tell your doctor immediately.
Vaginal discharge that is different than normal for you	Tell your doctor immediately.
Pain or a feeling of pressure in your pelvis or your bones	Tell your doctor immediately.
Read more about medicines and side effects and reporting a reaction you think might be a side effect.