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Combined oral contraceptive (1st-generation progestogen)

Ethinylestradiol with norethisterone

Brand names: Ovysmen, Loestrin, Brevinor

A combined oral contraceptive of ethinylestradiol with norethisterone, a first-generation progestogen.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

Ovulation is inhibited through hypothalamic-pituitary suppression, with added contraceptive effect from cervical mucus thickening and an endometrium made unfavourable to implantation.

Prescribing in practice

  • All combined hormonal contraceptives carry VTE and arterial risk; norethisterone preparations are among the lower-risk options, but UKMEC contraindications must still be screened.
  • Assess for migraine with aura, cardiovascular risk factors and thrombosis history before prescribing.
  • Advise on missed-pill rules and reduced efficacy with enzyme inducers or significant gastrointestinal upset.

Monitoring

Check blood pressure and reassess cardiovascular and VTE risk at initiation and at periodic review.

Counselling the patient

  • Take at the same time each day and follow missed-pill advice.
  • The pill does not protect against sexually transmitted infections.
  • Seek urgent help for calf swelling, chest pain, breathlessness or sudden severe headache.

Evidence & guidelines

MHRA and UKMEC document the relative VTE risks of combined pills by progestogen type, with first-generation progestogens among the lower-risk group.

Reference: FSRH CHC guideline; UKMEC; MHRA Drug Safety Update; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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