CONTRACEPTIVE EFFICACY OF LOW-DOSES OF MIFEPRISTONE

Objective: To determine whether a 5-mg dose of mifepristone is suffici ent to prevent pregnancy. Design: Clinical study. Setting: Academic re search center. Subject(s): Healthy, fertile, sexually active female vo lunteers. Intervention: Volunteers received a 5-mg dose of mifepriston e once weekly, starting on cycle day 2, for up to 6 months. This was t heir only contraceptive method. Main Outcome Measure(s): Number of pre gnancies. Result(s): The treatment resulted in a significant decrease in pregnancy rate without affecting the menstrual cycle or causing dis turbing side effects. Conclusion(s): A low dose of mifepristone, which does not inhibit ovulation, reduces fertility significantly by affect ing the endometrium. However, the contraceptive effect needs to be imp roved for the drug to compete with other contraceptive methods. (Ferti l Steril(R) 1998;70:813-6. (C) 1998 by American Society for Reproducti ve Medicine.).