OBJECTIVES: An open-label randomized trial (DAYANA) was conducted in sub-Saharan settings to evaluate four different regimens containing tenofovir disoproxil fumarate as first-line treatment for HIV infection. The objectives of the present substudy were to assess the relationship between trough concentrations of tenofovir in plasma collected after 24 h (C24) and estimated glomerular filtration rates (eGFR) calculated by the different formulae that are available. METHODS: The criteria for eligibility were those of the DAYANA trial, recruiting naive patients. The four tenofovir regimens were: Group 1, tenofovir/emtricitabine/nevirapine; Group 2, tenofovir/lopinavir/ritonavir; Group 3, tenofovir/emtricitabine/zidovudine; and Group 4, tenofovir/emtricitabine/efavirenz. The C24 of tenofovir was determined using LC-MS/MS. The eGFR was calculated using the Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulae. RESULTS: The median C24 of tenofovir was 42 ng/mL. The C24 of tenofovir was higher with lopinavir/ritonavir than with the other three regimens: at Week 4, 84 ng/mL versus 25 ng/mL; and at Week 48, 81 ng/mL versus 52 ng/mL. The baseline merged eGFR was 98.2 mL/min/1.73 m(2) with the CKD-EPI equation. Only the mean changes in eGFR in Group 2 differed from the absolute value of zero (-8.2 mL/min/1.73 m(2)) with the CKD-EPI equation between baseline and Week 48. The Cockcroft-Gault formula is inappropriate for these African patients because it underestimated the baseline eGFR and overestimated the changes in eGFR between baseline and Week 48. CONCLUSIONS: In this population of mostly female HIV-1-infected African patients, tenofovir plasma overexposure was associated with PI/ritonavir and a time-dependent decrease in eGFR, probably via an inhibition of MRP2/MRP4 efflux transporters. The close monitoring over time of the eGFR using MDRD or CKD-EPI calculations and by using other biomarkers of renal disorder should be proposed as an alternative to therapeutic drug monitoring in resource-limited countries.