Coadministration of raltegravir (400 mg twice daily) and atazanavir/ritonavir increased raltegravir AUC (41%), Cmax (24%) and Cmin (77%). However, concomitant use of twice daily raltegravir and atazanavir/ritonavir did not result in a unique safety signal in clinical studies, therefore, no dose adjustment of raltegravir is required when given twice daily. Coadministration of raltegravir (1200 mg single dose) and atazanavir alone increased raltegravir AUC (67%), Cmax (16%) and Cmin (26%). The US product label for raltegravir states that no dose adjustment is required with atazanavir/ritonavir and once daily raltegravir, however, the European label does not recommend coadministration with once daily raltegravir.