A Study of Continuous Oral Contraceptives and Doxycycline

The purpose of this study is to learn if the study drug, doxycycline, can decrease the amount of unplanned vaginal bleeding that women commonly experience when taking combined oral contraception (COC)- pills with estrogen and progestin - in a continuous fashion - no hormone-free week. The study drug, doxycycline, is an antibiotic used commonly for many conditions (i.e. acne, Chlamydia infections, pneumonia) and can be safely used on a daily basis. Doxycycline has been shown to decrease unplanned vaginal bleeding in progestin-only contraception but has not been studied in combined hormonal contraception.