Strong Cyp3a4 Inducers
Severe
Database
Markedly reduced progestin levels
Use additional/non-hormonal contraception
Source: Kimi deep-research + Cla
Drug reference
norethindrone
Progestin (19-nortestosterone derivative) · Contraceptive; Sex Hormone
START
POP: 0.35 mg PO once daily at same time; endometriosis 5 mg/day titrate
TYPICAL MAX
15 mg/day (endometriosis)
STOP IF
Thromboembolism, severe depression, hormone-sensitive cancer
WATCH
Bleeding pattern, BP, mood, breast symptoms, VTE signs
CDSCO approvedATC G03DC02
KDIGO 2024 + manufacturer label
- ONSET
- 1h · absorption
- PEAK
- 1.5h · Tmax
- t½
- 9h · t½
- DURATION
- 1d · once-daily
EXCRETION
Renal and faecal — metabolites
route + CYP
INTERACTIONS
1 major
SEVERE in our sources
PREGNANCY
Avoid in pregnancy (rare virilising effects on female fetus at high dose).
FDA category + note
Top interactionssee all 5 →
- Strong Cyp3a4 InducersSevereDatabaseKimi deep-research + Cla
Mechanism
Selective progesterone-receptor agonist with weak androgenic activity; suppresses LH surge / inhibits ovulation, thickens cervical mucus, alters endometrium — contraception, menstrual regulation, and progestin component of hormone therapy.
Indications
Oral contraception (progestin-only or combined)Abnormal uterine bleedingSecondary amenorrhoeaEndometriosisAdjunct in hormone replacement therapy (with oestrogen)
Dosing
- Adult
- Contraception (POP): 0.35 mg PO once daily at same time, continuously. Endometriosis: 5 mg/day for 2 weeks, increase by 2.5 mg/day every 2 weeks to 15 mg/day for 6–9 months. AUB: 5–10 mg/day for 5–10 days.
- Pediatric
- Not established (≥menarche per indication).
- Renal adjustment
- No specific adjustment.
- Hepatic adjustment
- Avoid in significant hepatic disease.
- Geriatric
- Postmenopausal HRT use specific.
- Max dose
- 15 mg/day (endometriosis ceiling)
Pharmacokinetics
Onset
Endometrial effect over days; contraception ~2 days continuous use
Peak effect
~1–2 h (Tmax)
Duration
~24 h (once-daily)
Half-life
~5–14 h
Bioavailability
~64% (high first-pass)
Protein binding
~80% (SHBG + albumin)
Metabolism
Hepatic CYP3A4 + reduction
Excretion
Renal (metabolites) and faecal
Contraindications
- Active venous thromboembolism
- Active or history of hormone-sensitive cancer (breast)
- Unexplained vaginal bleeding
- Significant hepatic disease
- Hypersensitivity
Side effects
Common
Irregular bleeding / spottingBreast tendernessHeadacheMood changeWeight changeAcne
Serious
- Thromboembolism (especially combined with oestrogen)
- Hepatic adenoma (rare)
- Severe depression
- Hypersensitivity / anaphylaxis
Pregnancy & lactation
Pregnancy
Avoid in pregnancy (rare virilising effects on female fetus at high dose).
Lactation
Progestin-only pills compatible from 6 weeks postpartum; combined pills delay.
Drug interactions
Lamotrigine
Moderate
Database
Reduced lamotrigine levels (combined OCs)
Adjust lamotrigine; monitor levels
Source: Kimi deep-research + Cla
Other Thromboembolism Risk Drugs
Moderate
Database
Additive VTE risk (with oestrogen)
Risk-assess; choose POP for higher-risk
Source: Kimi deep-research + Cla
Strong Cyp3a4 Inhibitors
Moderate
Database
Increased levels
Monitor
Source: Kimi deep-research + Cla
Warfarin
Moderate
Database
Variable effect
Monitor INR
Source: Kimi deep-research + Cla
Related guidelines
Ask House about norethindrone
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e·Verified: 2026-05-20 · House clinical team·Cockpit curated: 2026-05-20