title: Metabolism of tenofovir and didanosine in quiescent or stimulated human peripheral blood mononuclear cells.
abstract: OBJECTIVE
  As tenofovir disoproxil fumarate substantially increases plasma concentrations of didanosine in patients with human immunodeficiency virus-1 infection, we sought to determine whether tenofovir and didanosine showed a similar intracellular interaction in human peripheral blood mononuclear cells (PBMCs).
  
  
  METHODS
  Comparative in vitro incubation of two antiretrovirals in lymphocytes.
  
  
  METHODS
  Clinical research laboratory.
  
  
  METHODS
  Radiolabeled tenofovir and didanosine in human PBMCs.
  
  
  RESULTS
  Phosphorylation of 2 and 20 microM didanosine to dideoxyadenosine triphosphate (ddATP) was determined in quiescent and stimulated PBMCs in the presence or absence of 5 microM tenofovir. Similarly, phosphorylation of 5 microM tenofovir to tenofovir diphosphate (TFVpp) was examined in the presence or absence of 2 and 20 microM didanosine. Intracellular amounts of ddATP and TFVpp were determined by incubating PBMCs with radiolabeled tenofovir or didanosine alone and together for up to 16 hours and then separating the anabolites by high-performance liquid chromatography for quantitation. The presence of tenofovir did not affect the amount of ddATP in quiescent or stimulated PBMCs with 2 or 20 microM didanosine. In addition, didanosine did not alter the amount of TFVpp that formed. The amount of ddATP was modestly (1.5-3-fold) but consistently higher in stimulated than in quiescent PBMCs, but the amount of TFVpp did not differ.
  
  
  CONCLUSIONS
  There is no significant interaction between tenofovir and didanosine in human PBMCs as determined by the extent of formation of the phosphorylated anabolites. This suggests that adjusting didanosine dosage, when given with tenofovir, to achieve similar didanosine plasma concentrations, may be sufficient to accommodate the systemic drug interaction.
authors.affiliation: St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Robbins
authors.forename: Carrie K
authors.initials: CK
authors.lastname: Wilcox
authors.forename: Arnold
authors.initials: A
authors.lastname: Fridland
authors.forename: John H
authors.initials: JH
authors.lastname: Rodman
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D019380:Anti-HIV Agents / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media; D016049:Didanosine / Q000737:chemistry / Q000378:metabolism*; D004347:Drug Interactions; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D063065:Organophosphonates; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D000068698:Tenofovir
chemical_list: D019380:Anti-HIV Agents; D003470:Culture Media; D063065:Organophosphonates; D009943:Organophosphorus Compounds; D000068698:Tenofovir; D000225:Adenine; D016049:Didanosine