Is tenofovir involved in hypophosphatemia and decrease of tubular phosphate reabsorption in HIV-positive adults?

Objectives: Tubulopathy with hypophosphatemia have been observed in HIV-positive patients receiving a tenofovir-containing regimen. However, the real incidence and prevalence of hypophosphatemia and their relation to tubular reabsorption disorders in tenofovir-treated patients remain uncertain. The aim of our study was to explore the effect of tenofovir on phosphatemia and on tubular phosphate reabsorption. Methods: In a first transversal study, 145 HIV-positive adults (44 +/- 9 years) receiving tenofovir 300 mg daily with a mean exposure of 11 +/- 9 months were included. In a second prospective study, 29 HIV-positive antiretroviral experienced adults (44 +/- 10 years) were evaluated before introduction of tenofovir 300 mg daily (M0) and at 3 months (M3) and 6 months (M6), thereafter. Phosphate, creatinine, glucose and protein levels were determined in plasma and urine. The ratio of maximal, reabsorption capacity (TmP04)/glomerular filtration rate (GFR) was determined by using the normogramm of Walton and Bijvoet. Results: In the transversal study, 26% of patients had hypophosphatemia (< 0.84 mmol/l.) while 47% of patients had a decreased TmPO4/GFR (< 0.8 mmol/l). In the prospective study, baseline prevalence of hypophosphatemia (< 0.84 mmol/l) and decreased TmPO4/GFR (< 0.8 mmol/l) was 31 and 41%, respectively. Three and 6 months after starting tenofovir, there is no significant change in mean phosphate levels (M0:0.91 mmol/l., M3:0.97 mmol/l, M6:0.98 mmol/l) and mean TmPO4/GFR (M0:0.80 mmol/l, M3:0.88 mmol/l, M6:0.84 mmol/l). Moreover, prevalence of hypophosphatemia (M3:28%, M6:28%) and decreased TmPO4/GFR (M3:41%, M6:45%) remained stable. Conclusion: Hypophosphatemia linked to a decreased proximal tubular reabsorption was frequently observed in HIV-positive adults independently of the use of tenofovir.