A pilot study on the use of letrozole with either misoprostol or mifepristone for termination of pregnancy up to 63 days.

BACKGROUND Letrozole is a third-generation selective aromatase inhibitor. Animal data suggested that it might be useful in medical abortion. We performed two pilot studies to assess the feasibility of using letrozole in combination with either mifepristone or misoprostol for termination of pregnancy up to 63 days. STUDY DESIGN We recruited 40 subjects who requested legal termination of pregnancies up to 63 days. Medical abortion was performed with letrozole 7.5 mg daily for 2 days followed by 800 mcg vaginal misoprostol in 20 subjects and letrozole 7.5 mg combined with 200 mg mifepristone in another 20 subjects. RESULTS The mean induction-to-abortion interval of the regimen of letrozole and misoprostol was 9.1 h (median 7.9 h, range 2.7-23.6 h). The complete abortion rate was 80% (95% CI: 56.3-94.3%). For those with gestation of ≤ 49 days, the complete abortion rate was 87.5% (14/16; 95% CI: 61.7-98.5%). The mean induction-to-abortion interval of letrozole combined with mifepristone was 90.1 h (median 93.4 h, range 66.0-121.2 h). The complete abortion rate was 71.4% (95% CI: 47.8-88.7%). CONCLUSION These preliminary results suggest that a regimen of letrozole and misoprostol may be useful in medical abortion, but the combination with mifepristone is less effective and takes longer. Randomized studies comparing letrozole and misoprostol to misoprostol alone are warranted.