Pharmacokinetics and Pharmacodynamics of DMPA With HIV PrEP

The investigators hypothesize that a drug interaction exists between DMPA and tenofovir/emtricitabine, such that levels of tenofovir (TFV) and emtricitabine (FTC) in cervicovaginal fluid, rectal fluid, and blood plasma, and levels of the active metabolites of TFV and FTC in cervical tissue and peripheral blood mononuclear cells will be significantly lower when women are using DMPA than when they are using no hormonal contraception. The investigators secondarily hypothesize that ex vivo HIV replication will be less suppressed in cervical tissue and cervicovaginal fluid when women are using the co-formulated pre-exposure prophylaxis oral pill containing tenofovir disoproxil fumarate (TDF), the prodrug of tenofovir, and FTC concurrently with the contraceptive injection DMPA as compared to when they are on TDF/FTC alone. This study is a biphasic steady state pharmacokinetic and pharmacodynamic study of TFV and FTC in healthy women comparing the drug levels and activity in the absence (first phase) and then the presence (second phase) of DMPA. The investigators will recruit 12 healthy women aged 18-45 who are HIV-negative and at low risk for acquiring HIV. Participants will take TDF/FTC for 14 days, after which drug levels will be measured and DMPA administered. After at least a 2 week washout period for TDF/FTC, participants will again take TDF/FTC for 14 days, and drug levels will be measured again. HIV replication activity will also be measured in cervicovaginal fluid and cervical tissue at baseline before starting TDF/FTC, after 14 days of TDF/FTC, and then after the second 14 days of TDF/FTC in the presence of DMPA.