BMA Concise Guide to Medicine & Drugs

Norethisterone

Brand names Micronor, Noriday, Noristerat, Primolut N, Utovlan

Used in the following combined preparations Brevinor, Climagest, Loestrin, Norinyl, Synphase, TriNovum, and others

QUICK REFERENCE

Drug group Female sex hormone

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Norethisterone is a progestogen, a synthetic hormone similar to the natural female sex hormone, progesterone. It has a wide variety of uses including the postponement of menstruation and the treatment of menstrual disorders such as endometriosis. When used for these disorders, it is taken only on certain days during the menstrual cycle. In combination with oestrogens, it is also prescribed as hormone replacement therapy (HRT), which is usually only advised for short-term use around the menopause, and in the treatment of certain breast cancers. One of norethisterone’s major uses is as an oral contraceptive. It may be used on its own or with an oestrogen. It is also available in an injectable contraceptive preparation.

Adverse effects are rare, but oral contraceptives may cause breakthrough bleeding.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, injection, skin patch.

Frequency and timing of doses 1–3 x daily (tablets); once every 8 weeks (injection); 2 x weekly (skin patch).

Adult dosage range 10–15mg daily (menstrual disorders); 15mg daily (postponement of menstruation); 350mcg daily (progestogen-only contraceptives); 700mcg–1mg daily (HRT); 30–60mg daily (cancer).

Onset of effect The drug starts to act within a few hours.

Duration of action 24 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Take as soon as you remember. If you are taking the drug for contraception, see what to do if you miss a pill.

Stopping the drug The drug can be safely stopped as soon as contraceptive protection is no longer required. If prescribed for an underlying disorder, do not stop taking the drug without consulting your doctor. When the drug is used to treat menstrual disorders, a normal period should occur 2 to 3 days after it is stopped.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.

POSSIBLE ADVERSE EFFECTS

Adverse effects of norethisterone are rarely troublesome and are generally typical of progestogens. The most common adverse effect is breakthrough bleeding, which should be discussed with your doctor. More rarely, the drug may cause swelling of the ankles or feet, weight gain, acne, and discoloration of the skin. Discuss with your doctor if these are severe or if you have headaches or depression. If you experience pain or tightness in the chest, or disturbances of vision or hearing, stop taking the drug and contact your doctor immediately. Rarely, prolonged treatment may cause jaundice due to liver damage; if jaundice occurs, stop taking the drug and contact your doctor. However, prolonged use is not generally recommended because of the increased health risks (see Prolonged use).

INTERACTIONS

General note Norethisterone may interfere with the beneficial effects of many drugs, including oral anticoagulants, anticonvulsants, antihypertensives, and drugs for diabetes. Many other drugs may reduce the contraceptive effect of norethisterone-containing pills. These include anticonvulsants, antituberculous drugs, certain antivirals, antibiotics, and St John’s wort. Be sure to inform your doctor that you are taking norethisterone before taking additional prescribed medication.

Ciclosporin Levels of ciclosporin may be raised by norethisterone.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have liver or kidney problems.

· You have diabetes.

· You have had epileptic seizures.

· You suffer from migraine.

· You have acute porphyria.

· You have heart or circulatory problems, especially a history of venous thrombosis.

· You are taking other medicines.

Pregnancy Not usually prescribed. May cause defects in the baby. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Not prescribed.

Over 60 Not usually prescribed.

Driving and hazardous work No special problems.

Alcohol No special problems.

Surgery and general anaesthetics Inform your doctor or dentist that you are taking norethisterone. He or she will tell you when to stop taking it prior to any surgery.

PROLONGED USE

As part of HRT, norethisterone is usually only advised for short-term use after the menopause. It is not normally recommended for long-term use or for treating osteoporosis. HRT increases the risk of venous thrombosis and breast cancer. The breast cancer risk reduces after stopping the drug, disappearing entirely after 10 years.

Monitoring Blood-pressure checks and physical examination, including regular mammograms, may be performed.