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Coadministration of raltegravir (400 mg twice daily) and unboosted atazanavir (300 mg twice daily) was studied in 22 HIV-positive volunteers. Raltegravir pharmacokinetics were compared to historical data from HIV-positive volunteers receiving 10 day raltegravir monotherapy.

Raltegravir geometric mean AUC with atazanavir was 6166 ng.h/ml and was comparable to historical controls (6851 ng.h/ml). Atazanavir exposure showed high inter subject variability with a geometric mean AUC of 14622 ng.h/ml and a CV of 68.3%. Linear regression showed a highly significant correlation between raltegravir AUC and atazanavir AUC: subjects with atazanavir AUC >14622 ng.h/ml had a two-fold increase in raltegravir AUC. A similar trend was observed for trough concentrations.

Overall, unboosted atazanavir did not significantly increase raltegravir exposure, although subjects with higher atazanavir exposure had higher raltegravir concentration.

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Raltegravir pharmacokinetics are variable and this is a cross study comparison; therefore we need to be cautious in interpreting the data.

Ref: Cattaneo D et al. Exposure-related effects of unboosted atazanavir on the pharmacokinetics of raltegravir in HIV-1 infected patients. 11th PK Workshop, 2010. Abstract 49.