Intracellular tenofovir-diphosphate concentrations in HIV pre-exposure prophylaxis users who underwent bariatric surgery

ObjectiveTo measure concentrations of tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) among individuals taking tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC) or tenofovir alafenamide plus emtricitabine (TAF/FTC) who were scheduled to undergo or had already undergone bariatric surgery.MethodsWe enrolled pre-exposure prophylaxis (PrEP) users attending clinics in Toronto or Ottawa who were undergoing or had undergone bariatric surgery. After participants completed a minimum of 7 days of consecutive PrEP dosing, we collected DBS samples immediately before they administered their next daily dose of PrEP. Participants who had already undergone bariatric surgery before enrolment provided a single sample at baseline only. One participant undergoing planned bariatric surgery provided samples preoperatively and on postoperative days 7, 28 and 84. TFV-DP was measured by liquid chromatography tandem mass spectrometry. We compared results against the population range TFV-DP at varying degrees of adherence and stratified by chronology of bariatric surgery, type of bariatric surgery and PrEP regimen.ResultsOf seven eligible participants, all were gay, cis-gender men. Median age was 48 years (Q1-Q3: 44-51). Six participants underwent bariatric surgery before enrolment: four Roux-en-Y gastric bypass (RYGB) and two sleeve gastrectomy (SG). Four were taking TDF/FTC and two were taking TAF/FTC. All had therapeutic TFV-DP concentrations, except for one TDF/FTC participant who underwent SG. One participant taking TAF/FTC enrolled before receiving RYGB and displayed a slight decrease in TFV-DP over time, although all concentrations remained in the therapeutic range.ConclusionsTenofovir diphosphate concentrations were at or near therapeutic values in this small sample of men using oral PrEP who underwent RYGB or SG.