A randomized trial of superovulation with two different doses of letrozole

Objective: The aim of this study was to evaluate the effects of either a 2.5-mg or a 5-mg daily dose of letrozole in women undergoing superovulation and intrauterine insemination (IUI). Design: Prospective randomized trial. Setting: Academic teaching hospital. Patient(s): Women <40 years old, with patent fallopian tubes and infertility of >1 year in duration. Intervention(s): Patients were randomized into either a 2.5-mg dose of letrozole (34 patients) or a 5-mg dose of letrozole (38 patients) daily for 5 days. When the leading follicle reached 18 mm in diameter, ovulation was triggered by an injection of hCG and IUI was performed 24 and 48 hours later. Main Outcome Measure(s): The number of follicles, endometrial thickness, and pregnancy rate. Result(s): Compared with those treated with 2.5 mg of letrozole, the total number of follicles was significantly higher in patients receiving 5 mg of letrozole. No difference in the endometrial thickness was found between the two groups. The pregnancy rate per cycle in patients receiving 5mg of letrozole was statistically higher than in patients receiving 2.5 mg of letrozole (26.3% vs. 5.9%, P<.05). No multiple pregnancies occurred. Conclusion(s): Compared with the daily dose of 2.5 mg, 5 mg of letrozole is associated with more follicles and a higher pregnancy rate. It appears that 5 mg daily for 5 days is a preferable letrozole dose for superovulation.