A Study of Continuous Oral Contraceptives and Doxycycline

We intend to conduct a prospective, randomized, placebo controlled, double blind study at Oregon Health and Science University. This study will be conducted over four 28-day cycles (112 days of active COC hormone). All women enrolled in the study will take the same daily low dose COC. This protocol will be divided into two studies, a bleeding study and an endometrial biopsy study, each with two treatment arms; typical dose doxycycline (Arm 1), and controlled release subantimicrobial dose doxycycline (CRSD)(Arm 2). The first arm (Arm 1) of this study will constitute the typical dose doxycycline arm. In this arm, there will be two study groups. Group 1, the treatment group, will take doxycycline 100 mg orally twice a day for five days starting on the first day of bleeding if breakthrough bleeding occurs. The control group will take a placebo orally twice a day for five days starting on the first day of bleeding if breakthrough bleeding occurs. After three months, both groups will stop doxycycline (or placebo) and will continue on a COC alone for the remaining 28 days of the study. The second arm (Arm 2) of the study will constitute the controlled release subantimicrobial dose doxycycline (CRSD doxycycline)arm. Subjects in this arm of the study will be divided into Group 3 and Group 4. Group 3 will take CRSD doxycycline (40mg) daily for three months. Group 4 will take a daily placebo. Similarly to the first arm of the trial, after three months, both groups will stop doxycycline (or placebo) and will continue in a COC alone for the remaining 28 days of the study. This study also includes a endometrial biopsy sub-study: At the time of recruitment we will identify participants who are willing to undergo endometrial biopsy during the study period. These subjects will constitute a separate cohort who will enroll in the prospective, randomized, double blind, placebo controlled endometrial biopsy study.