Effective antiretroviral therapy (ART) depends on adequate drug exposure. Plasma ART concentrations provide a short-term assessment of drug exposure, and hair promises to be an alternative matrix for measuring long-term exposure. We aimed to determine the association between plasma and hair ART concentrations and explore the therapeutic concentrations in hair. A cohort study in which HIV-infected adults receiving tenofovir disoproxil fumarate (TDF) + lamivudine (3TC) + efavirenz (EFV) regimen for at 6 months were recruited and paired hair and plasma samples collected at about 6±1 months of ART. Previously validated liquid chromatography and tandem mass spectrometry methods were used to measure ART concentrations in plasma and hair. Among 74 participants enrolled, 47 used a 400 mg dose of EFV daily and 27 used 600 mg EFV daily. Hair and plasma EFV concentrations were strongly correlated, with particularly strong association observed in the 600 mg EFV group. The hair EFV concentration of female participants was significantly higher than in male participants, which might be the inter-individual variations in the drug metabolism and dissolution and life habits. The concentrations of TDF and 3TC in hair are too low to determine effective threshold and relationship with plasma drugs concentrations. The accumulation and correlation of hair and plasma EFV concentrations promise to determine a therapeutic range in hair. The therapeutic range for EFV in hair needs to be calculated in order to give quantitative results more value within the field of drug exposure assessment.
