title: Intracellular and plasma steady-state pharmacokinetics of raltegravir, darunavir, etravirine and ritonavir in heavily pre-treated HIV-infected patients.
abstract: OBJECTIVE
  To study the steady-state plasma and intracellular pharmacokinetics of raltegravir, etravirine, darunavir and ritonavir in heavily pre-treated patients.
  
  
  METHODS
  Patients on a salvage regimen containing raltegravir, etravirine, darunavir and ritonavir were eligible for inclusion. During a 12 h dosing interval plasma and peripheral blood mononuclear cells were collected. Drug concentrations were measured using a validated LC-MS/MS assay and pharmacokinetic analysis was performed using non-linear mixed effect modelling.
  
  
  RESULTS
  Irregular absorption was observed with raltegravir and darunavir, which may be caused by enterohepatic cycling. Relative bioavailability of ritonavir was low, when compared with other ritonavir regimens. Raltegravir plasma pharmacokinetics showed wide interpatient variability, while intracellular raltegravir concentrations could not be detected (<0.001 mg l(-1) in cell lysate). The intracellular to plasma ratios for etravirine, darunavir and ritonavir were 12.9, 1.32 and 7.72, respectively, and the relative standard error of these estimates were 16.3%, 12.3% and 13.0%.
  
  
  CONCLUSIONS
  The observed distinct intracellular accumulation indicated that these drugs have different affinity for the cellular compartment. The relatively high intracellular accumulation of etravirine may explain its efficacy and its previously described absence of PK-PD relationships in the therapeutic concentration range, when compared with other non-nucleoside reverse transcriptase inhibitors. Lastly, the intracellular concentrations of ritonavir seem sufficient for inhibition of viral replication in the cellular compartment in PI-naive patients, but not in patients with HIV harbouring PI resistance.
authors.affiliation: Department of Pharmacy & Pharmacology, Slotervaart Hospital, Amsterdam, the Netherlands. rob@terheine.nl
authors.forename: Rob
authors.initials: R
authors.lastname: Ter Heine
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Mulder
authors.forename: Eric C M
authors.initials: EC
authors.lastname: van Gorp
authors.forename: Jiri F P
authors.initials: JF
authors.lastname: Wagenaar
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
authors.forename: Alwin D R
authors.initials: AD
authors.lastname: Huitema
mesh_terms: D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000069454:Darunavir; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D009570:Nitriles; D011724:Pyridazines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use; D011743:Pyrimidines; D019438:Ritonavir / Q000008:administration & dosage / Q000493:pharmacokinetics; D016879:Salvage Therapy; D013449:Sulfonamides / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use
chemical_list: D019380:Anti-HIV Agents; D009570:Nitriles; D011724:Pyridazines; D011743:Pyrimidines; D013449:Sulfonamides; C451734:etravirine; D019438:Ritonavir; D000069454:Darunavir