Comparison of Administration of Letrozole 20 mg Single Dose Versus 25 mg in Divided Doses to Stimulate Ovulation in IUI Cycles

Although letrozole has been used for ovulation disorders in intra-uterine insemination (IUI) for a long time, the dose and method used have not been determined.

This randomized clinical trial was conducted in 200 eligible infertile women who were candidates for IUI. They were randomly divided into two groups: in the first group, a single dose of 20 mg of letrozole tablet prescribed on the third day of the cycle, and in the second group, on the third to the seventh days of the cycle, 5 mg of letrozole tablets were prescribed every day (in total, 25 mg in divided doses). The patients underwent transvaginal ultrasound on days 9–11 of the cycle, and the size of the follicles and the thickness of the endometrium were examined and if the patient's follicles were suitable, IUI was performed.

137 patients (69%) had one or more follicles higher than 14 mm. The mean (SD) diameter of the largest follicle and endometrial thickness were 15.0 ± 2.9 mm and 5.5 ± 1.4 mm, respectively, which were not significantly different between the two groups (P > 0.05). Pregnancy occurred in 62 patients (31%) and in 10 patients (5%) abortion occurred in the first trimester with no significant difference between the two groups (P > 0.05).

Prescribing letrozole 20 mg as a single dose on the third day of the cycle to stimulate ovulation in IUI cycles has comparable effects with 5 divided doses of 5 mg on the third to seventh days of the cycle.