Norethisterone with mestranol

How it works

Mestranol (a prodrug converted to ethinylestradiol) and norethisterone together suppress gonadotrophin release to inhibit ovulation, while also thickening cervical mucus and altering the endometrium.

Prescribing in practice

• As a combined oestrogen-containing preparation it raises the risk of venous and arterial thromboembolism and is contraindicated where this risk is high, such as migraine with aura, established cardiovascular disease, or smoking in older women.
• Efficacy may be reduced by enzyme-inducing drugs, and the woman should be assessed against UK Medical Eligibility Criteria before starting.
• Counsel on what to do about missed pills and that additional precautions may be needed in certain situations.

Monitoring

Check blood pressure and review thrombotic and cardiovascular risk factors before starting and periodically during use.

Counselling the patient

• Take it regularly and follow the missed-pill instructions to keep contraceptive cover.
• Stop and seek urgent care for severe leg pain or swelling, chest pain, breathlessness, or sudden severe headache or visual change.
• Tell your clinician about migraines with aura, smoking, and any new medicines.

Evidence & guidelines

Combined oral contraceptives are prescribed in line with the UK Medical Eligibility Criteria and Faculty of Sexual and Reproductive Healthcare guidance.