Effect of letrozole on uterine tonus and contractility: a randomized controlled trial

Letrozole inhibits estrogen production. It has been shown to increase efficacy in medical abortion when used with misoprostol. This study investigated if letrozole acts as an abortifacient due to a synergistic effect with misoprostol on uterine contractility.

Sixteen healthy women requesting surgical abortion were randomized to receive either no pretreatment or treatment with letrozole 7.5 mg daily for 3 days prior to the abortion. All women received misoprostol 400 mcg vaginally 3.5 h prior to surgery. Intrauterine pressure was measured for 30 min before and 3.5 h after misoprostol was given using an intrauterine pressure catheter. Main outcome measure was uterine contractility analyzed by repeated-measures analysis of variance.

At baseline, uterine contractions were absent and tonus was low. No significant difference was seen between the two groups in tonus (p=.818) or in contractility (p=.423) after misoprostol administration.

Letrozole does not appear to act as an abortifacient through an effect on uterine contractility or increased sensitivity to misoprostol of the uterine myometrium.