Raloxifene | Cancer Research UK
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What raloxifene is

Raloxifene is a type of drug called a selective oestrogen receptor modulator (SERM). These drugs act very like the female sex hormone oestrogen although they aren’t hormones.


How raloxifene works

Many breast cancers are stimulated to grow by the hormones oestrogen and progesterone. These breast cancers are called hormone sensitive or hormone receptor positive cancers. Oestrogen locks on to a protein called the oestrogen receptor in the breast cancer cell. This stimulates the cell to divide and grow. Raloxifene binds to the oestrogen receptor and stops oestrogen from making the cell divide.

Research has shown that taking raloxifene can lower the risk of breast cancer in women who are at high or moderate risk of developing it. The National Institute for Health and Care Excellence (NICE) has recommended raloxifene as  an option to reduce risk for women who are at moderate or high risk and have had their menopause. It is not suitable for women who have had their womb removed (a hysterectomy).

Raloxifene is also a way to prevent and treat bone thinning (osteoporosis) in women who have had their menopause. Oestrogen helps to keep the bones strong. After the menopause women have less oestrogen in their body and some develop osteoporosis.


How you have raloxifene

Raloxifene is a tablet that you take once a day. You should swallow it whole. You can choose the best time to take it but you need to take it at about the same time every day. You may take it with or without food. If you are taking it to reduce the risk of breast cancer you take it for 5 years.

It is very important that you take tablets according to the instructions your doctor or pharmacist gives you. You should take the right dose, not more or less. And never stop taking a cancer drug without talking to your specialist first.

We've listed the side effects associated with raloxifene below. You may have 1 or 2 or a few of them. You can use the links to find out more about each side effect. Where there is no link, please see our cancer drug side effects section or use the search box at the top of the page.


Common side effects

More than 10 in every 100 people have one or more of the side effects listed below.

  • Hot flushes and sweats affect 1 in 4 people (25%)
  • Leg cramps affect 1 in 4 people (25%)
  • Flu like symptoms happen in about 2 out of 10 people (20%)
  • Abdominal pain

Occasional side effects

Between 1 and 10 in every 100 people have one or more of these effects.

  • Fluid retention that may cause ankle and or finger swelling (or weight gain) occurs in about 3 out of 100 people (3%)
  • Headaches
  • A low sex drive
  • Feeling sick – this is usually mild but let your doctor or nurse know if you have it

Rare side effects

Fewer than 1 in 100 people have these effects.

  • A slightly increased risk of blood clots (thrombosis) – if you or a close relative have had a blood clot in the past tell your doctor
  • Bruising or bleeding more easily due to a drop in the number of platelets in the blood
  • Breast tenderness and pain – this is usually mild
  • An increase in breast size

Important things to remember

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment. Sometimes more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)
  • Other drugs you are having

Coping with side effects

Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them. You should have a contact number for your clinic. You can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

Other medicines

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together.


More information about raloxifene

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at www.medicines.org.uk.

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at www.mhra.gov.uk.

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Updated: 6 February 2014