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About norethisterone

Norethisterone and the contraceptive pill

Women currently taking a contraceptive pill should not use norethisterone to delay their period.

If using the combined contraceptive pill continuing a new packet straight after your last month's packet will delay your period. However, you cannot do this if taking progestogen-only contraceptive pill (mini pill) or a combined pill which contains dummy (non-active) pills at the end of the pill pack. The way to delay your period depends on the type of combined pill you take - read NHS - How can I delay my period? for further information.

Norethisterone is NOT a contraceptive and will not prevent pregnancy. It should not be taken in pregnancy.

Norethisterone and other contraceptives

Norethisterone can be used with any non-hormonal contraceptive e.g. coil (IUD) or barrier methods such as condoms and caps.

It should not be used alongside any hormonal contraception including pills, patches, the vaginal ring, implant, contraceptive depot injection, and hormone releasing coils. Consult your own GP or contraception advisor about delaying periods whilst taking these contraceptives.

What is norethisterone?

Norethisterone is a man-made form of progesterone, a naturally occurring female sex hormone and is used for a number of medical conditions. It cannot be used as hormone replacement therapy (HRT). Medium-strength tablets can treat heavy periods and are even used for some female cancers, such as breast cancer.

Norethisterone is no longer under patent and is produced by many pharmaceutical companies.

How does norethisterone work?

In a natural female cycle the menstrual period (monthly shedding of the womb lining) is triggered by a drop in female hormone levels. Norethisterone keeps the hormone levels high and delays the period until after the norethisterone tablets have been stopped and hormone levels drop.

When should you take norethisterone?

Norethisterone 5mg tablets can be taken three times daily to delay periods. Start tablets at least 3 days before the expected start of a period and continue for as long as needed. A period bleed will normally start 2 to 3 days, and possibly longer, after stopping norethisterone.

For how long should I take norethisterone?

Dr Fox can supply a maximum of 60 tablets to delay a period for up to 17 days. Fewer tablets are required to delay periods for less than 17 days.

Norethisterone is only designed to be taken occasionally and should not be requested more than once every 3 months. If you need to delay a period for more than 17 days, or more often, you should consult your GP.

Possible side effects of norethisterone

All medications are prone to causing side effects and you're more likely to suffer them if you take norethisterone long-term, but the most common side effects are:

• Bloating
• Breast tenderness
• Loss of libido
• Jaundice (yellowing of the skin due to liver disease)
• Fluid retention which may worsen pre-existing migraine, high blood pressure, epilepsy, or asthma

In rare cases norethisterone can cause a severe allergic reaction. Early symptoms of this include difficulty breathing, wheezing, feeling faint, swelling of the tongue or face, intense and itchy skin rash, and swelling of the hands and feet. Seek emergency medical care immediately - telephone 999 in the UK.

You can read more about potential side effects in the manufacturer's patient information leaflet supplied with norethisterone tablets.

Taking other medications

Consult your doctor before taking norethisterone if you regularly take any of the following, as the effectiveness of either medication may be affected:

• Medicines to treat epilepsy (e.g. phenytoin, carbamazepine)
• Antibiotic medicines to treat an infection (e.g. tetracyclines, rifampicin, co-trimoxazole)
• Antiviral medicines to treat HIV (e.g. ritonavir, nelfinavir)
• Anticancer medicines
• Herbal preparations containing St John's Wort (Hypericum perforatum)
• Ciclosporin (for suppressing the immune system)
• Non-steroidal inflammatory drugs (NSAIDs) for treating pain and inflammation
• Medicines for high blood pressure

Other cautions to consider

Blood clots in the veins or legs are a common risk for all women and these risks are slightly increased when taking norethisterone, especially if you're very overweight, have suffered previous blood clots in the veins or lungs, have relatives with blood clots, have been immobile for long periods (after an operation, or a long haul flight, for example), have suffered serious injury or major surgery, or have a history of repeated miscarriage, or are travelling to high altitude.

Many women prefer to take Provera for period delay as the increased blood clotting risk is lower than with norethisterone.

Norethisterone should not be taken during pregnancy or when breastfeeding.

There are a few other conditions where it may be advised against using norethisterone for period delay. Checks are carried out in the online assessment. Please consult your GP if you are unsure.