title: Is tenofovir involved in hypophosphatemia and decrease of tubular phosphate reabsorption in HIV-positive adults?
abstract: OBJECTIVE
  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 (TmPO4)/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 (<0.8mmol/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.
  
  
  CONCLUSIONS
  Hypophosphatemia linked to a decreased proximal tubular reabsorption was frequently observed in HIV-positive adults independently of the use of tenofovir. In this preliminary study, no worsening effect on phosphatemia and tubular phosphate reabsorption was observed 6 months after introduction of tenofovir in treatment experienced patients.
authors.affiliation: Department of Biochemistry, University Hospital, F34295 Montpellier, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Badiou
authors.forename: Corinne Merle
authors.initials: CM
authors.lastname: De Boever
authors.forename: Nathalie
authors.initials: N
authors.lastname: Terrier
authors.forename: Vincent
authors.initials: V
authors.lastname: Baillat
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Cristol
authors.forename: Jacques
authors.initials: J
authors.lastname: Reynes
mesh_terms: D000225:Adenine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000328:Adult; D019380:Anti-HIV Agents / Q000009:adverse effects* / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D017674:Hypophosphatemia / Q000139:chemically induced*; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000009:adverse effects* / Q000627:therapeutic use; D010710:Phosphates / Q000378:metabolism; D000068698:Tenofovir
chemical_list: D019380:Anti-HIV Agents; D063065:Organophosphonates; D010710:Phosphates; D000068698:Tenofovir; D000225:Adenine