Letrozole (Ovulation Induction)

How it works

Letrozole is an aromatase inhibitor that blocks conversion of androgens to oestrogens, reducing oestrogen negative feedback so that pituitary FSH secretion rises and drives follicular development.

Prescribing in practice

• It is used in the days before conception and must be confined to the recommended early-cycle course while pregnancy is excluded, as letrozole is not for use once pregnancy is established.
• There is a possibility of multiple pregnancy, though generally lower than with some other ovulation-induction agents, and cycles should be monitored.
• Common effects include hot flushes, fatigue and headache during the treatment course.

Monitoring

Monitor the ovulatory response, for example with ultrasound tracking or mid-luteal progesterone, to confirm ovulation and guide subsequent cycles.

Counselling the patient

• Take the tablets only on the specific cycle days advised, then stop.
• Confirm timing of intercourse or further tests with your fertility team.
• Hot flushes and tiredness during the course are common and temporary.

Evidence & guidelines

Randomised trial evidence and NICE-endorsed practice support letrozole as an effective ovulation-induction agent in polycystic ovary syndrome, with comparable or better live-birth outcomes than clomifene in this group.