Characterization of Doxycycline Pharmacokinetics and Adherence

The purpose of this study is to evaluate the effect of body changes on doxycycline concentrations for different dosing schedules. This study will involve a single dose phase and a multiple dose phase. Healthy individuals who do not have a sexually transmitted infection (STI), including acute (e.g., gonorrhea or chlamydia) or chronic (e.g., HIV or HSV-2) infections will be enrolled in this study. Study participants will be randomized to a dosing schedule in each phase and come to the research clinic throughout their time on study for sample collection. Study participants that choose to enroll in this study will be enrolled for about 37 days.