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Synthetic Progestogen Pregnancy: Contraindicated — potential risk of virilisation of female fetus at high doses (androgenic progestogen). Stop if pregnancy confirmed.

Norethisterone

Brand names: Primolut N, Utovlan

Adult dose

Dose: Dysfunctional uterine bleeding / HMB: 5mg TDS for 10 days; bleeding stops within 24–48h. To postpone menstruation: 5mg TDS starting 3 days before expected period — continue until postponement complete; period begins 2–3 days after stopping. Endometriosis: 10–15mg OD continuously for 4–6 months. HRT (progestogen component, in combined HRT): 1mg OD (licensed formulations).
Route: Oral
Frequency: Two to three times daily (most indications)
Max: 15mg OD (endometriosis); 5mg TDS (bleeding control)
At doses used for postponement and HMB, norethisterone is NOT effective as a contraceptive — do not rely on it for contraception. Used as HRT progestogen component but micronised progesterone (Utrogestan) preferred for lower cardiovascular and breast cancer risk.

Paediatric dose

Route: Oral
Frequency: Two to three times daily
Max: Individualised
Used in adolescents with severe menorrhagia or endometriosis under specialist supervision. Seek specialist paediatric/adolescent gynaecology opinion.

Dose adjustments

Renal

No specific dose adjustment required.

Hepatic

Avoid in severe hepatic disease — norethisterone is hepatically metabolised.

Clinical pearls

  • VTE warning: norethisterone 5mg TDS for HMB carries significantly higher VTE risk than the progestogen-only pill (small contraceptive doses) — advise risk-benefit discussion, especially in obese patients or those with personal/family VTE history
  • Menstrual postponement for special events (holidays, exams): must start 3 days BEFORE expected period — if started after period begins, it will not stop ongoing menstruation
  • Not a contraceptive at doses used for HMB or postponement — counsel patients clearly
  • Micronised progesterone (Utrogestan) preferred for HRT as progestogen component — better cardiovascular and breast safety profile than norethisterone

Contraindications

  • Active liver disease or hepatic tumours
  • History of VTE (norethisterone at high doses has androgenic properties and weak oestrogenic effects — increases VTE risk at high doses)
  • Undiagnosed vaginal bleeding
  • Breast or endometrial cancer (active)
  • Arterial disease

Side effects

  • Irregular spotting
  • Nausea
  • Breast tenderness
  • Fluid retention
  • Mood changes / depression
  • Acne and hirsutism (androgenic effects)
  • VTE (higher risk at doses used for HMB vs. contraceptive doses)

Interactions

  • Enzyme-inducing drugs — reduce efficacy
  • Warfarin — variable effect on INR; monitor

Monitoring

  • Bleeding pattern
  • Blood pressure
  • Liver function if prolonged use
  • VTE risk assessment

Reference: BNFc; BNF 90; NICE NG88 (Heavy Menstrual Bleeding); FSRH Guideline. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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