Synthetic Progestogen
Pregnancy: CONTRAINDICATED — androgenic progestogen; theoretical risk of virilisation of female fetus; not to be used if pregnancy is possible
Norethisterone
Brand names: Primolut N, Utovlan
Adult dose
Dose: HMB: 5 mg three times daily D19-26 of cycle; Endometriosis: 10-15 mg daily D5-25; Period delay: 5 mg three times daily starting 3 days before expected period
Route: Oral
Frequency: Three times daily (indication-dependent)
Max: 15 mg/day
Short-term period delay, HMB, endometriosis; NOT a contraceptive at these doses; breakthrough bleeding common with endometriosis regimen initially
Paediatric dose
Dose: Not established; adolescent endometriosis off-label specialist use N/A/kg
Route: N/A
Frequency: N/A
Max: N/A
Not licensed under 18 years for most indications
Dose adjustments
Renal
No dose adjustment required
Hepatic
Contraindicated in severe hepatic impairment or liver disease
Paediatric weight-based calculator
Not licensed under 18 years for most indications
Clinical pearls
- NICE NG88 (Heavy Menstrual Bleeding): norethisterone 5 mg TDS D19-26 is a short-term option for cyclical HMB — levonorgestrel IUS (Mirena) is preferred first-line for long-term HMB management with superior efficacy and fewer androgenic side effects
- Androgenic properties of norethisterone explain acne, oily skin, and mild virilisation risk — 4th generation progestogens (dienogest) have superior tolerability profile for endometriosis; norethisterone remains widely used due to low cost and availability
- Period delay: widely requested for holiday/events — counsel that withdrawal bleed occurs 2-3 days after stopping; efficacy is not 100%; NOT contraceptive; do not prescribe if pregnancy possible
- VTE risk: norethisterone acetate in HRT combinations (e.g. in Ryeqo) carries class VTE risk — oral norethisterone for gynaecological indications carries same risk; lower risk than combined OCP but counsel accordingly
- Endometriosis regimen: higher doses (10-15 mg/day) achieve pseudo-decidualisation and amenorrhoea; major side effect burden vs GnRH agonists or dienogest — ESHRE does not recommend norethisterone as preferred first-line endometriosis treatment
Contraindications
- Current or history of VTE
- Liver disease
- Arterial disease (angina, MI, stroke)
- Undiagnosed vaginal bleeding
- Hormone-sensitive cancers
Side effects
- Irregular bleeding/spotting
- Nausea
- Breast tenderness
- Acne/androgenic effects
- Fluid retention
- VTE risk (androgen-derived progestogen)
- Mood changes
Interactions
- CYP3A4 inducers (rifampicin, anticonvulsants) — reduce levels; reduced contraceptive/therapeutic effect
- Ciclosporin — norethisterone inhibits ciclosporin metabolism; increased ciclosporin levels
Monitoring
- Symptom response
- Menstrual diary
- Blood pressure
- VTE symptoms (calf pain, breathlessness)
Reference: BNFc; BNF 90; NICE NG88 (Heavy Menstrual Bleeding 2018); ESHRE Endometriosis Guideline (2022); SPC Primolut N; RCOG Clinical Governance Advice No. 6. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.