Medroxyprogesterone tablets: uses, side effects and cautions

Medroxyprogesterone is a progestogen. It behaves in the way the hormone progesterone does in your body, only more strongly. The tablets are sold in the UK under the names Provera and Climanor and are available on prescription only.

The NHS lists several reasons for prescribing it: heavy periods, endometriosis, polycystic ovary syndrome (which the NHS now calls PMOS), menopause symptoms, and hot flushes caused by prostate cancer treatments. High-dose formulations are also used in cancer treatment, which is a separate specialist use.

For period problems the tablets thin the lining of the womb and help to regulate when bleeding happens. In hormone replacement therapy they stand in for declining hormone levels during the menopause.

The NHS says the tablets start working immediately. Symptoms should improve within the first month, although full benefit can take 2 or 3 months.

Most adults, and girls who have started their periods, can take medroxyprogesterone tablets. The prescriber needs to know before you begin if you have any of these:

• An earlier allergic reaction to medroxyprogesterone or another medicine.

• Pregnancy, plans to become pregnant, or breastfeeding.

• Porphyria, a rare condition.

• A current or family history of hormone-sensitive cancer, such as some breast cancers.

• Past liver problems.

• A deep vein thrombosis or a clot in the lungs.

• A meningioma, which is a type of brain tumour.

• High blood pressure, previous heart attack or angina.

• Mental health problems, migraines, diabetes, epilepsy, asthma, gallstones or lupus.

• Hearing loss caused by otosclerosis.

The pattern depends on the reason. The NHS gives examples such as 2.5mg to 10mg once a day for 5 to 10 days of the cycle for period problems, 10mg three times a day for 3 months for endometriosis, 10mg once a day for 14 days every 1 to 3 months for PMOS, and 20mg once a day for hot flushes from prostate cancer treatment, usually for 10 weeks at first. HRT doses vary from person to person. Your own prescription is the one to follow.

Swallow the tablets with water, with or without food. Take once-daily doses at the same time each day and space three-times-daily doses evenly. Courses for period problems and endometriosis are usually short, over 2 to 3 months, and the prescriber reviews whether to continue.

A missed dose should be taken when remembered unless the next is close, in which case skip it; never double up. Missing doses can cause breakthrough bleeding or spotting. If you take more than prescribed, call NHS 111 for advice.

More than 1 in 100 people have common effects, including headaches, nausea, irregular bleeding or spotting, weight gain, breast tenderness, mood changes such as nervousness or low mood, trouble sleeping, a raised body temperature, dizziness, tiredness, itchy skin, acne, hair loss and changes to vaginal discharge.

Serious effects affect fewer than 1 in 1,000. They are a clot in the leg or arm (pain, swelling, redness and warmth), a clot in the lungs (breathlessness, chest pain, coughing, sometimes blood), sudden loss of vision in one or both eyes, and anaphylaxis.

• Call 999 for suspected lung clots, sudden loss of vision or a severe allergic reaction, and do not drive yourself to A&E.

• Call NHS 111 for signs of a clot in a leg or arm.

• Report suspected side effects through the Yellow Card scheme.

Do not take medroxyprogesterone tablets while pregnant. The lower doses (2.5mg, 5mg, 10mg) are unlikely to harm a baby if taken unknowingly in early pregnancy, but stop and speak to a doctor if you find you are expecting. It is safe to use while breastfeeding at usual doses, since only small amounts reach the milk, though high-dose cancer treatment needs specialist advice.

The tablets can reduce fertility while you take them, and fertility usually returns after you stop. They are not reliable contraception, so the NHS says to use a non-hormonal method such as condoms.

The NHS lists medicines that can change how medroxyprogesterone works: rifampicin, HIV and hepatitis C medicines, the epilepsy medicines carbamazepine, phenytoin, phenobarbital and primidone, and warfarin. St John's wort must not be taken with it.

Alcohol is fine. If the tablets make you dizzy or tired, do not drive, cycle or use tools until you feel better. After each monthly course, or at the end of treatment, you will usually have a period; tell your doctor if none comes, because that can mean pregnancy. Meals can be eaten as usual.