Anastrozole or letrozole for ovulation induction in clomiphene-resistant women with polycystic ovarian syndrome: a prospective randomized trial

Objective

To compare the effects of letrozole (2.5 mg) and anastrozole (1 mg) meant for ovulation induction in clomiphene (CC)-resistant women with PCOS.

Design

Prospective randomized trial.

Setting

University teaching hospital and private practice setting.

Patient(s)

The study comprised a total of 220 infertile women (574 cycles) with CC-resistant PCOS.

Intervention(s)

Patients were randomized to treatment with 2.5 mg of letrozole daily (111 patients, 295 cycles) or 1 mg of anastrozole daily (109 patients, 279 cycles) for 5 days from day 3 of menses.

Main Outcome Measure(s)

Number of follicles, serum E₂, serum P, endometrial thickness, pregnancy rate (PR), and miscarriage rate.

Result(s)

The total number of follicles was significantly more in the anastrozole group (5.4 ± 0.4 vs. 5.8 ± 0.4). The number of follicles ≥14 mm (3.1 ± 0.3 vs. 2.7 ± 0.2) and ≥18 mm (2.3 ± 0.1 vs. 3.1 ± 0.2) were significantly higher in the anastrozole group. The endometrial thickness at the time of hCG administration was significantly more in the anastrozole group (9.1 ± 0.2 vs. 10.2 ± 0.7 mm). The duration to reach a dominant follicle was longer in the letrozole group (12.1 ± 1.3 days vs. 8.8 ± 1.9 days) but without statistical significant difference. Ovulation occurred in 183/295 cycles (62%) in the letrozole group and 177/279 cycles (63.4%) in the anastrozole group, whereas pregnancy occurred in 36/295 cycles (12.2%) in the letrozole group and 42/279 cycles (15.1%) in the anastrozole group and the differences were not statistically significant.

Conclusion(s)

The results of this study did not show a significant difference in PR or miscarriage rate between anastrozole and letrozole when used for ovulation induction in women with CC-resistant PCOS.

Key Words: Letrozole, anastrozole, PCOS