Single Dose Truvada Study

To establish the plasma and peripheral blood mononuclear cells (PBMC) concentrations of TFV and TFV diphosphate (TFV-DP), respectively, following a single oral dose of Truvada® \[300 mg tenofovir disoproxil fumarate (TDF) in fixed dose combination with emtricitabine (FTC)\], the same formulation used for HIV pre-exposure prophylaxis (PrEP), and in prior benchmarking adherence studies (HPTN 066). This will be compared to steady-state TFV and TFV-DP concentrations to more robustly differentiate single dose concentrations from steady-state concentrations. This is part of a larger project to determine the frequency of white coat adherence in several clinical studies where doses are not observed. For purposes of diagnosing WCA with TDF, the investigators define WCA quantitatively as taking a single dose of TDF preceded by no doses in the prior week. The investigators will compare TFV and TFV-DP concentrations following an observed single oral dose of TDF/FTC to steady-state concentrations of TFV and TFV-DP after daily dosing under observation. The study plan involves a screening visit to assess eligibility, followed by two study visits. Visit one involves pre-dose blood testing, followed by a single dose of Truvada. Visit two occurs 24-hours after visit one, and involves collection of a final post-dose blood sample. Blood will be assessed for tenofovir and tenofovir analyte concentrations.