[A randomized multicentre clinical trial on different doses of mifepristone alone and in combination with anordrin as emergency contraception]

Abstract

Objectives: To investigate the effectiveness and side-effects of different doses of mifepristone alone or in combination with anordrin given orally within 96 hours after unprotected intercourse as an emergency contraceptive.

Methods: 2,400 cases of healthy women were recruited and allocated randomly in 4 groups: single dose of 25 mg mifepristone, 25 mg mifepristone plus 7.5 mg anordrin, 10 mg mifepristone plus 5 mg anordrin and 10 mg mifepristone alone. The efficacy rates of contraception were estimated according to Dixon method.

Results: The total expected number of pregnancy was 171.9 for 2,387 subjects enrolled in the study. The number of observed pregnancies related to method failure was 32 cases. The contraceptive effectiveness rates for the above 4 groups were 80.9%, 85.3%, 90.6% and 67.3%, respectively. For the group received 10 mg mifepristone plus 5 mg anordrin, pregnancy rate was 0.7% which was significantly lower than that in 10 mg mifepristone alone group (2.2%, P < 0.05). The incidences of withdrawal bleeding were 9.2%, 4.9%, 3.4% and 6.7% for the 4 group respectively. Two groups received mifepristone in combination with anordrin showed significant lower incidence of withdrawal bleeding than those in mifepristone alone groups.

Conclusion: Single oral administration of 25 mg mifepristone alone, and the combination of 10 mg mifepristone plus 5 mg anordrin were safe and effective treatment regimen for emergency contraception with no serious adverse reaction and disturbance on menstrual pattern.