No change in calculated creatinine clearance after tenofovir initiation among Thai patients

Objectives: Thai patients have a lower average body weight than patients from western Europe or the USA. Tenofovir is largely prescribed at the standard dosage of 300 mg once daily: therefore, the per kilogram dose is higher in Thailand than in the USA. We asked the question whether this higher per kilogram dose was associated with more nephrotoxicity. Methods: Thai patients from the Staccato trial were treated with tenofovir/lamivudine combined with ritonavir-boosted saquinavir. Creatinine values were measured before the start of tenofovir and then every 12 weeks. Renal function was assessed using the Cockcroft-Gault formula and the MDRD formula. To compare CLCR before and after tenofovir, the t-paired or Wilcoxon signed rank tests were used. One-way analysis of variance and Spearman's correlation coefficient were used to study CLCR longitudinally. Results: CLCR remained stable after a median of 21 weeks on tenofovir (difference of +1.06 mL/min; 95% CI - 2.7-4.8, P = 0.58), even among patients with underlying diseases. The mean CLCR remained stable across time (P = 0.17). Conclusions: We did not find renal dysfunction on tenofovir among Thai patients included in the Staccato trial. Tenofovir could be safely prescribed at a standard dosage of 300 mg once daily in the Thai population.