Clomiphene citrate combined with metformin versus letrozole for induction of ovulation in clomiphene-resistant polycystic ovary syndrome: a randomized clinical trial.

A total of 202 patients with clomiphene citrate (CC) -resistant polycystic ovary syndrome (PCOS) were randomly allocated into two arms of induction of ovulation; the first group (n = 102) received CC 100 mg and metformin 500 mg while the second group (n = 100) received letrozole 2.5 mg with ovulation rate, clinical pregnancy rate, adverse effects, and acceptability were assessed. Patients in the letrozole arm experienced higher rate of ovulation (82% versus 43.1%, p < .001), more dominant follicles (p < .05), better endometrial thickness (p < .001), higher clinical pregnancy rate (36% versus 9.8%, p < .001), higher multiple pregnancy rate (p < .05), lesser adverse effects (p < .05) and higher acceptability (p < .001) compared to patients in the CC and metformin arm. In conclusion; letrozole is better and more acceptable than combined CC and metformin for inducing ovulation in patients with CC-resistant PCOS with higher clinical pregnancy rate and unexpectedly higher multiple pregnancy rate.