Boosted saquinavir hard gel formulation exposure in HIV-infected subjects: ritonavir 100 mg once daily versus twice daily.
OBJECTIVE
The amount of ritonavir needed to enhance saquinavir hard gel (hg) plasma concentrations is unclear. Reduced ritonavir dosing may help to reduce ritonavir-related side effects and costs. This study examined the pharmacokinetics of twice-daily saquinavir-hg (1000 mg) in the presence of ritonavir 100 mg, dosed twice-daily and once-daily on one single occasion.


METHODS
Eighteen HIV-infected adults taking saquinavir/ritonavir 1000/100 mg twice-daily underwent pharmacokinetic (PK) assessment of saquinavir/ritonavir on day 1 following a morning saquinavir/ritonavir dose. On day 2, PK assessment was repeated when subjects took saquinavir without ritonavir. Drug intake (with a standard meal containing 20 g of fat) was timed on days -1, 1 and 2. Geometric mean ratios (GMR) and 95% confidence intervals (CI) were calculated to assess changes in saquinavir PK parameters.


RESULTS
Geometric mean saquinavir AUC(0-12), C(trough), C(max) and elimination half-life on days 1 and 2 were 14 389 and 9590 ng.h/mL, 331 and 234 ng/mL, 2503 and 1893 ng/mL and 2.80 and 2.82 h, respectively. The GMR (95% CI) for these parameters were 0.67 (0.53-0.84), 0.71 (0.48-1.04), 0.76 (0.58-0.98) and 1.01 (0.86-1.18), respectively.


CONCLUSIONS
Withholding a ritonavir dose significantly reduces overall saquinavir exposure and C(max), but had no impact on the elimination half-life. These data establish the need to administer saquinavir and ritonavir simultaneously.
Boffito
Marta
M
PK Research Ltd, St Stephen's Centre, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK. marta.boffito@chelwest.nhs.uk
Maitland
Desmond
D
Dickinson
Laura
L
Back
David
D
Hill
Andrew
A
Fletcher
Carl
C
Moyle
Graeme
G
Nelson
Mark
M
Gazzard
Brian
B
Pozniak
Anton
A
D019540:Area Under Curve; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D006801:Humans; D008297:Male; D010865:Pilot Projects; D019438:Ritonavir / Q000008:administration & dosage* / Q000494:pharmacology* / Q000627:therapeutic use; D019258:Saquinavir / Q000008:administration & dosage* / Q000493:pharmacokinetics* / Q000627:therapeutic use
D019258:Saquinavir; D019438:Ritonavir