First-lineFemara
Letrozole
Aromatase inhibitor
Now preferred first-line over clomifene for ovulation induction in PCOS.
Oral
First-line for
- Anovulatory PCOS (NICE 2024 first-line)
- Breast cancer (non-pregnancy)
Mechanism
Blocks aromatase → ↓ oestrogen → ↑ FSH → follicle growth. Shorter half-life than clomifene — less endometrial thinning.
Letrozole vs Clomifene
- L — Live birth ↑ in PCOS
- E — Endometrium spared
- T — Twins less common
Dosing
- Dose
- 2.5 mg OD day 2–6
- Escalate
- 5 → 7.5 mg if no response
- Max
- 5 mg most cycles
Contraindications
- AbsolutePregnancy (avoid)
- CautionSevere hepatic impairment
Side effects
- Hot flushes
- Headache
- Fatigue
- Arthralgia
Fetal & maternal notes
- • Not teratogenic at ovulation-induction doses (large studies).
- • Stop once pregnancy confirmed.
Key interactions
Tamoxifen
CautionAntagonism
Clinical pearls
- 💡 Off-label for fertility in UK but recommended by NICE 2024.
- 💡 Better live-birth rates in PCOS vs clomifene (PPCOS II).
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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