Effective switching to atazanavir/ritonavir in clinical practice

Simon Collins, HIV i-Base

In a second study, Paul Holmes and colleagues at the Chelsea and Westminster Hospital, London, presented results from clinical use of atazanavir in 241 patients since June 2004. Of note, 231 patients used boosted atazanavir and only 10/241 used unboosted atazanavir (ATZ).

In this retrospective case note review 89 patients were PI-naïve, 47 were single PI-experienced and 105 were had used 2 or more prior PIs.

Around half these patients changed to ATZ due to previous treatment failure. The other half switched due to toxicity or adherence difficulties with the current regimen while fully suppressed (with a viral load <50 copies/ml). Switched drugs for tolerability/adherence included Kaletra (34), saquinavir/ritonavir (22), other PI (14) and efavirenz (38).

100% and 95% of patients switching with a viral load <500 or <50 copies/ml respectively at week four maintain this level of suppression to week 12.

50% and 62% of PI-naïve and PI-experience patients changing treatment due to virological failure (viral load >50 copies/ml) had viral load <50 copies/ml at week 12, although durability of response is clearly the important factor here and this was shown in this short study.

Bilirubin increased by 28.5 umol/L at week 12 and was >25 umoll/L in 68% patients. However there were only 12 discontinuations only four of which were related to jaundice. Other discontinuations were due to virological failure (3), diarrhoea (2), abacavir reaction (1) and patient request (2).

This study provides encouraging support for successfully using at atazanavir/ritonavir in people needing to switch antiretrovirals whether they were PI naïve or PI experienced.


Holmes P, Randell P, Bower M et al. Clinical experience with atazanavir. 7th ICDTHI,14-18 Nov, 2004, Glasgow. Abstract P22.

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