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AIDS. 2017 Oct 23;31(16):2245-2251. doi: 10.1097/QAD.0000000000001615.

Hair levels of preexposure prophylaxis drugs measure adherence and are associated with renal decline among men/transwomen.

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aDepartment of Medicine, Division of HIV, Infectious Diseases, and Global Medicine bDepartment of Medicine, Center for AIDS Prevention Studies cDepartment of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California dDepartment of Medicine, Whitman-Walker Health, George Washington University School of Medicine, Washington, DC eDepartment of Medicine, Miller School of Medicine, University of Miami, Miami, Florida fSan Francisco Department of Public Health, San Francisco, California gSchool of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, Colorado, USA.



The US preexposure prophylaxis (PrEP) Demonstration Project (U.S. Demo) evaluated MSM on PrEP postmarketing and found low seroconversion rates. The objective of this study is to examine hair levels as an adherence measure to PrEP.


Using an 'opt-in' design, participants of PrEP Demo were invited to enroll into a substudy where hair was collected quarterly.


Tenofovir concentrations were measured in hair by liquid chromatography/tandem mass spectrometry. Hair levels consistent with ≥4 doses/week (protective in other studies) defined adequate adherence. Mixed effects multivariate logistic regression models examined factors associated with ≥4 doses/week. Separate mixed effects models evaluated the relationship between hair PrEP levels and changes in creatinine clearance (CrCl) over time.


Overall, 58% of U.S. Demo participants enrolled into this opt-in study; reasons for nonparticipation included insufficient hair (61%) and concerns about hairstyle (27%). Hair and dried blood spots levels consistent with ≥4 doses/week were highly concordant (84%). Hair levels showed adequate adherence in 87% of 875 person-visits (among 280 participants). Factors associated with adequate adherence in multivariate models were amphetamine use [adjusted odds ratio (aOR) 2.59 (0.97-6.9, P 0.06)], condomless receptive anal sex [aOR 2.28 (1.19-4.40, P 0.01)], and stable housing [aOR 2.63 (1.03-6.67), P 0.04]. Hair levels of tenofovir showed a monotonic relationship with decline in CrCl (P 0.01 for trend).


In this substudy of the U.S. PrEP demonstration project, hair and dried blood spots levels were highly concordant and hair concentrations demonstrated adequate adherence 87% of the time, with stable housing and high-risk behavior associated with higher adherence. Daily PrEP drug taking is associated with modest declines in CrCl.

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