Control of menstrual bleeding disturbances in women using Implanon contraception

This is a randomised, controlled, double-blind trial of the effectiveness of four active treatments and placebo in the management of episodes of breakthrough bleeding in women using the progestogen-only, sub dermal implant contraceptive, Implanon. Implanon provides the near-zero-order release of the progestogen, etonogestrel, over a three year period. Treatment will be randomised to one of five arms. Each treatment will be given twice daily for 5 days in a complex arrangement which allows the following measurements: 1 Mifepristone 25mgs taken twice on day 1 followed by 4 days of ethinyl oestradiol, 20 micrograms each morning and placebo each evening. 2 Doxycycline 100mgs taken twice daily for 5 days. 3 Doxycycline 100mg plus ethinyl oestradiol 20 micrograms in the morning, and doxycycline 100 mg in the evening, for 5 days. 4 Doxycycline 100mg plus mifepristone 25mg twice on the first day and then doxycycline 100 mg taken twice daily for 4 days. Each of these blinded treatments will be taken once a month for 3 months.