Randomized controlled trial of three doses of letrozole for ovulation induction in patients with unexplained infertility

The aromatase inhibitor letrozole is a novel agent that can be used as an alternative to clomiphene citrate for ovulation induction in patients with unexplained infertility. The dose of letrozole used has varied between studies, and this study aimed to compare the three most commonly used doses: 2.5, 5 and 7.5 mg. A total of 179 patients were randomly recruited in this prospective study with 58, 61 and 60 patients in each dosage group respectively. This study reports a significantly higher (P < 0.05) number of follicles (total, >14 mm and ≥18 mm) on the day of administration of human chorionic gonadotrophin in the 7.5 mg group, associated with significantly fewer (P < 0.05) days of stimulation. However the pregnancy and miscarriage rates were similar in the three groups. In conclusion, it seems that the use of higher doses of letrozole offers no advantage in terms of pregnancy rates over the lower (2.5 mg) dose.