Mifepristone ovarian function study

The aim is to determine whether the administration of mifepristone alone or in combination with ethinyl oestradiol will effect the contraceptive efficacy of Implanon whose main mode of action is ovulation suppression and a secondary effect on cervical mucus making it impenatrable to sper. Both the treaments we will use have been shown to have a beneficial effect on bleeding patterns in women using progestogen-only contraceptive methods. Bleeding problems are the major reason for women discontinuing these highly effective contraceptives.Eligible women will be randomised to either mifepristone followed by 4 days of placebo or mifepristone followed by four days of ethinyl oestradiol. Women will undergo vaginal ultrasound to assess follicular size, assessment of cervical mucus quality and have blood taken for serum levels of oestradiol and progesterone 2 days before commencing treatment, on the third treatment day, 6 days after starting treament and then twice weekly for 3 weeks. Women will be required to use condoms for the duration of the study.