Ritonavir boosting may not overcome interaction between atazanavir and nevirapine

A poster by Christopher S Alexander and colleagues from the British Columbia Centre for excellence in HIV/AIDS, Vancouver, Canada, looked at the interaction between atazanavir/ritonavir (ATZ/rtv) and nevirapine (NVP) and/or tenofovir (TDF) as observed in a clinical setting. The results suggest that RTV boosting of ATV reduces the interaction with TDF but it may not do the same with NVP.

It is recommended to boost ATZ with RTV (300/100mg) when administered with TDF but the interaction between NVP and ATZ has not previously been reported. Alexander and colleagues looked at HIV-positive adults taking regimens that included ATZ/rtv once daily. After at least two weeks of treatment, blood samples were taken at the Ctrough and 1, 2 and 3 hours post dose.

There was no significant difference in the median ATZ concentrations for those on ATZ/rtv only or for those also taking TDF. But the researchers did observe a trend towards reduced ATV concentrations in patients who also took NVP with or without TDF.

Alexander C, Montaner J, Langridge S et al. Interaction between atazanavir/ritonavir (ATV/rtv) and nevirapine (NVP) is observed in a clinical setting. 7th ICDTHI,14-18 Nov, 2004, Glasgow. Abstract P275.