JAC Advance Access originally published online on September 19, 2006
Journal of Antimicrobial Chemotherapy 2006 58(5):1009-1016; doi:10.1093/jac/dkl379
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Influence of atazanavir 200 mg on the intracellular and plasma pharmacokinetics of saquinavir and ritonavir 1600/100 mg administered once daily in HIV-infected patients
1 Department of Pharmacology and Therapeutics, University of Liverpool 70 Pembroke Place, Liverpool L69 3GF, UK 2 PK Research Ltd., St Stephen's Centre, Chelsea and Westminster Hospital 369 Fulham Road, London SW10 9NH, UK
Received 30 May 2006; returned 19 July 2006; revised 18 August 2006; accepted 18 August 2006
*Corresponding author. Tel: +44-2088466507; Fax: +44-2087465628; E-mail: marta.boffito{at}chelwest.nhs.uk
Objectives: To examine cellular and plasma concentrations of atazanavir when given in combination with saquinavir/ritonavir in HIV+ patients.
Methods: Twelve HIV+ patients were receiving saquinavir/atazanavir/ritonavir 1600/200/100 mg once daily and venous blood samples were taken to determine cellular and plasma concentrations of each protease inhibitor at 2, 6, 12 and 24 h. Peripheral blood mononuclear cells were separated by density gradient centrifugation. The ratio of the cellular AUC0–24/plasma AUC0–24 was calculated to determine cellular drug accumulation. Lymphocyte P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and multidrug resistance-associated protein (MRP1) expression was determined by flow cytometry. Nine of the patients had previously received a regimen of saquinavir/ritonavir 1600/100 mg; therefore the effect of atazanavir on the cellular and plasma pharmacokinetics of saquinavir and ritonavir was examined.
Results: In vivo cellular and plasma determinations of saquinavir, atazanavir and ritonavir gave accumulation ratios of 4.9, 1.2 and 1.7, respectively. There was no relationship between saquinavir, atazanavir or ritonavir accumulation and P-gp, MRP1 or BCRP expression. When comparing pharmacokinetic values in the nine patients receiving saquinavir/ritonavir with and without atazanavir, the median cellular saquinavir AUC0–24 was significantly increased (34.9–117.2 mg·h/L) on addition of atazanavir (P = 0.004). The C24 of saquinavir in plasma and cells was significantly higher with atazanavir (plasma C24 0.05 versus 0.14 mg/L with atazanavir; cellular C24 0.61 versus 2.03 mg/L with atazanavir, P = 0.02).
Conclusions: The mechanism of differential intracellular protease inhibitor accumulation is unclear. Co-administration of atazanavir caused an increase in both the plasma and cellular exposure (AUC0–24) and C24 of saquinavir but not ritonavir.
Keywords: protease inhibitors , intracellular pharmacokinetics , antivirals
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