['Lipid-based nutrient supplements (LNSs) are increasingly used in HIV programmes in resource-limited settings. However, the possible effects of LNSs on the plasma concentrations of antiretroviral drugs have not been assessed. Here, we aimed to assess the effects of LNSs on plasma efavirenz and nevirapine trough concentrations in Ethiopian adult HIV-infected patients.', 'The effects of LNSs were studied in adults initiating antiretroviral therapy (ART) in a randomized trial. Patients with body mass index (BMI) >\u200917\u2009kg/m(2) (n\u2009=\u2009282) received daily supplementation of an LNS containing whey (LNS/w), an LNS containing soy (LNS/s) or no LNS. Trough plasma concentrations of efavirenz and nevirapine were measured at 1 and 2 months. Genotyping for 516 G>T and 983 T>C polymorphisms of the cytochrome P450 (CYP) 2B6 locus was performed. Multilevel linear mixed-effects models were used to assess the associations between LNS and plasma efavirenz and nevirapine concentrations.', 'In patients with BMI >\u200917\u2009kg/m(2), nevirapine concentrations were lower in the LNS/w and LNS/s groups by a median of -2.3\u2009μg/mL [interquartile range (IQR) -3.9; -0.9\u2009μg/mL; P\u2009=\u20090.002] and -2.1\u2009μg/mL (IQR -3.9; -0.9\u2009μg/mL; P\u2009=\u20090.01), respectively, compared with the group not receiving supplements. There were no differences between groups with respect to efavirenz plasma concentrations. The CYP2B6 516 G>T polymorphism was associated with a 5\u2009μg/mL higher plasma efavirenz concentration compared with the wild type (P\u2009<\u20090.0001), while it was not associated with plasma nevirapine concentrations.'] Do lipid-based nutrient supplements affect efavirenz but lower plasma nevirapine concentrations in Ethiopian adult HIV patients?