Megestrol acetate (Megace ®)
Megestrol acetate is a type of hormonal therapy and is also called Megace®. It is usually used to treat breast cancer that has spread, but can sometimes be used to treat other cancers. In this section, we refer to it by its more commonly used name, Megace.
This section describes Megace, how it’s given and some of its possible side effects. The information should ideally be read with our general information about your type of cancer.
You’ll see your doctor regularly while you have this treatment so they can monitor its effects. This information should help you discuss any queries about your treatment and its side effects with your doctor or specialist nurse.
Megace is a hormonal therapy, which is similar to the female hormone progesterone.
Hormones are substances that are produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs.
The way that Megace works is not yet fully understood, but it's thought that it interferes with the action of particular female hormones in the body.
Many breast cancers rely on sex hormones, such as oestrogen, to grow. The cancer cells have proteins called receptors that sex hormones attach to.
When oestrogen comes into contact with the receptors, it fits into them and stimulates the cancer cells to divide so that the tumour grows.
Megace disrupts this process in some way. It may be that it prevents the cancer cells from maintaining the receptors on their surface. Alternatively, it may have a more direct way of destroying cancer cells that hasn’t been identified yet.
Megace is a 160mg tablet. The tablet is scored (partially cut) so it's possible to break it and take a lower dose.
It's commonly taken once a day but can be prescribed in smaller doses to be taken at regular intervals during the day. It can be taken with or after food and should be taken with a glass of water. When a single daily dose is prescribed it should be taken at the same time each day.
When it's prescribed in divided doses (to be taken more than once per day), the doses should be evenly spaced.
Megace is mainly used as a treatment for breast cancer in women whose cancer has returned after having been successfully controlled with other hormonal therapies such as tamoxifen.
Megace may also be given to women whose cancer hasn’t responded to other hormonal therapies, but whose cancer cells have oestrogen receptors on their surface.
Megace is sometimes used to treat cancer of the womb and occasionally to treat prostate cancer.
It can also be prescribed to reduce hot flushes in women during the menopause, and in men who have hot flushes as a result of treatment for prostate cancer.
Megace can help stimulate appetite, so it's sometimes helpful for people who have eating problems due to advanced cancer.
Possible side effects of Megace
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Each person's reaction to any medicine is different. Some people have very few side effects while others may experience more.
We have outlined the most common side effects but haven't included those that are rare and therefore unlikely to affect you. If you notice any effects that are not listed here, discuss them with your doctor or nurse.
Very rarely, if side effects are severe, you may have to stop taking Megace and a different hormonal drug may be prescribed.
The most commonly reported side effect is an increase in appetite, causing some people to put on weight. Dieting can help to control this, but you should consult your doctor before making any changes to your diet.
For people who have experienced weight loss as a result of their cancer, an increased appetite can be a beneficial effect.
Some people experience mild ankle swelling caused by fluid retention. This is not harmful but can be uncomfortable.
Feeling sick (nausea)
Occasionally people feel sick for the first few weeks of taking Megace, but this usually goes away.
You may experience mood swings or feel anxious. Talk to your doctor if this continues.
Always let your doctor or nurse know about any side effects you have. There are usually ways in which they can be controlled or improved.
Additional information about Megace
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Megace should not be taken during pregnancy. Even though women may find that their periods stop while taking Megace, it is not a contraceptive, so reliable contraception must be used during treatment. Vaginal bleeding (spotting) may occur when you stop taking Megace. This usually stops after a short time.
Blood sugar levels
People with diabetes will need to monitor their blood sugar more closely and may need to adjust their anti-diabetic medication while having Megace. Contact your doctor if you have any problems controlling your diabetes.
Risk of blood clots
People who have a history of blood clots should discuss this with their doctor before taking Megace. Rarely, it increases the risk of getting a clot.
If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you are having hormonal treatment. You should tell them the name of your cancer specialist so they can ask for advice.
It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home.
Things to remember about Megace tablets
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Megace may interact with other medicines. Tell your doctor about any medication you are taking including non-prescribed drugs such as complementary therapies and herbal drugs.
Keep the tablets in a safe place, out of the reach of children.
If your doctor decides to stop the treatment, return any remaining tablets to the pharmacist. Do not flush them down the toilet or throw them away.
Don't worry if you forget to take your tablet. Do not take a double dose. The levels of the drug in your blood will not change very much, but try not to miss more than one or two tablets in a row.
Remember to get a new prescription a few weeks before you run out of tablets and make sure that you have plenty for holidays.
This information has been compiled using information from a number of reliable sources, including:
British National Formulary. 64th edition. 2012. British Medical Association and Royal Pharmaceutical Society of Great Britain.
electronic Medicines Compendium (eMC). http://www.medicines.org.uk (accessed September 2012).
Sweetman, et al. Martindale: The Complete Drug Reference. 37th edition. 2011. Pharmaceutical Press.
With thanks to: Bruce Burnett, Teacher Practitioner in Clinical Pharmacy Practice; and the people affected by cancer who reviewed this edition. Reviewing information is just one way you could help when you join our Cancer Voices network.