title: Amprenavir and lopinavir pharmacokinetics following coadministration of amprenavir or fosamprenavir with lopinavir/ritonavir, with or without efavirenz.
abstract: BACKGROUND
  Amprenavir (APV), fosamprenavir (FPV), lopinavir (LPV), ritonavir (RTV) and efavirenz (EFV) are to varying degrees substrates, inducers and inhibitors of CYP3A4. Coadministration of these drugs might result in complex pharmacokinetic drug-drug interactions.
  
  
  METHODS
  Two prospective, open-label, non-randomized studies evaluated APV and LPV steady-state pharmacokinetics in HIV-infected patients on APV 750 mg twice daily + LPV/RTV 533/133 mg twice daily with EFV (n=7) or without EFV (n=12) + background nucleosides (Study 1) and after switching FPV 1,400 mg twice daily for APV (n=10) (Study 2).
  
  
  RESULTS
  In Study 1 EFV and non-EFV groups did not differ in APV minimum plasma concentration (Cmin; 1.10 versus 1.06 microg/ml, P = 0.89), area under the concentration-time curve (AUC; 17.46 versus 24.34 microg x h/ml, P = 0.22) or maximum concentration (Cmax; 2.61 versus 4.33 microg/ml, P = 0.08); for LPV there was no difference in Cmin, (median: 3.66 versus 6.18 microg/ml, P = 0.20), AUC (81.84 versus 93.75 microg x h/ml, P = 0.37) or Cmax (10.36 versus 10.93 microg/ml, P = 0.61). In Study 2, after switching from APV to FPV, APV Cmin increased by 58% (0.83 versus 1.30 microg/ml, P = 0.0001), AUC by 76% (19.41 versus 34.24 micorg x h/ml, P = 0.0001), and Cmax by 75% (3.50 versus 6.14, P = 0.001). Compared with historical controls, LPV and RTV pharmacokinetics were not changed. All treatment regimens were well tolerated. Seven of eight completers (88%) maintained HIV-1 RNA <400 copies/ml 12 weeks after the switch (1 lost to follow up).
  
  
  CONCLUSIONS
  EFV did not appear to significantly alter APV and LPV pharmacokinetic parameters in HIV-infected patients taking APV 750 mg twice daily + LPV 533/133 mg twice daily. Switching FPV 1400 mg twice daily for APV 750 mg twice daily resulted in an increase in APV Cmin, AUC, and Cmax without changing LPV or RTV pharmacokinetics or overall tolerability.
authors.affiliation: Johns Hopkins Hospital, Baltimore, MD, USA. vpham@jhmi.edu
authors.forename: Paul A
authors.initials: PA
authors.lastname: Pham
authors.forename: Craig W
authors.initials: CW
authors.lastname: Hendrix
authors.forename: Patricia
authors.initials: P
authors.lastname: Barditch-Crovo
authors.forename: Teresa
authors.initials: T
authors.lastname: Parsons
authors.forename: Wasif
authors.initials: W
authors.lastname: Khan
authors.forename: Michelle
authors.initials: M
authors.lastname: Parish
authors.forename: Christine
authors.initials: C
authors.lastname: Radebaugh
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Carson
authors.forename: Gary E
authors.initials: GE
authors.lastname: Pakes
authors.forename: Roula
authors.initials: R
authors.lastname: Qaqish
authors.forename: Charles
authors.initials: C
authors.lastname: Flexner
mesh_terms: D000328:Adult; D000480:Alkynes; D019380:Anti-HIV Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D048588:Benzoxazines / Q000008:administration & dosage / Q000627:therapeutic use; D002219:Carbamates / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics* / Q000627:therapeutic use; D003521:Cyclopropanes; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D005663:Furans; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology; D017320:HIV Protease Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D006801:Humans; D061466:Lopinavir; D008297:Male; D008875:Middle Aged; D010755:Organophosphates / Q000008:administration & dosage / Q000627:therapeutic use; D011744:Pyrimidinones / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019438:Ritonavir / Q000008:administration & dosage / Q000627:therapeutic use; D013449:Sulfonamides / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D002219:Carbamates; D003521:Cyclopropanes; D005663:Furans; D017320:HIV Protease Inhibitors; D010755:Organophosphates; D011744:Pyrimidinones; D013449:Sulfonamides; D061466:Lopinavir; C095108:amprenavir; C098320:efavirenz; D019438:Ritonavir; C426859:fosamprenavir