Combined Oral Contraceptive Pill (COCP)

How it works

It primarily inhibits ovulation by suppressing pituitary gonadotrophin release, with additional effects of thickening cervical mucus and altering the endometrium.

Prescribing in practice

• It carries an increased risk of venous and arterial thromboembolism, so prescribing requires assessment against UK Medical Eligibility Criteria and is avoided where risk factors such as migraine with aura are present.
• Effectiveness can be reduced by enzyme-inducing drugs and by vomiting or severe diarrhoea, requiring additional precautions.
• Blood pressure should be checked before starting and contraception reviewed if new risk factors develop.

Monitoring

Monitor blood pressure and periodically reassess cardiovascular and thrombotic risk factors and the chosen method.

Counselling the patient

• Seek urgent help for symptoms of a clot such as calf swelling, chest pain or breathlessness.
• Use extra precautions if you miss pills, vomit or have severe diarrhoea, or start an interacting medicine.
• Report new or worsening migraine, especially with aura, as this may mean the pill is no longer suitable.

Evidence & guidelines

UK Medical Eligibility Criteria for Contraceptive Use guide safe prescribing and contraindications for combined hormonal contraception.