As reported in the August 12 issue of HIVandHepatitis.com, Chelsea Castellano presented data on the incidence of and risk factors for tenofovir-associated nephrotoxicity at the XVII International AIDS Conference last week in Mexico City.

In her slide presentation, she reported that 7.5% of patients taking tenofovir (Viread, also in the Truvada and Atripla combination pills) developed nephrotoxicity, compared with 4.2% of those taking antiretroviral regimens that did not include tenofovir.

The study investigators have since pointed out a mathematical error in the presentation: 35 of 744 patients taking tenofovir developed kidney toxicity, which works out to 4.7% -- not 7.5% -- meaning the rates were actually comparable in the tenofovir and non-tenofovir groups.

The corrected results, which indicate little difference in rates of kidney toxicity in patients taking or not taking tenofovir, are in agreement with another study presented at the conference. In this retrospective analysis of more than 300 HIV patients -- a majority of whom were black, a group at higher risk for kidney disease -- there was no observed association between tenofovir use and nephrotoxicity. However, the risk was significantly higher among older patients and those with high blood pressure (abstract THPE0182).

On the other hand, a cross-sectional analysis of nearly 700 patients in the SUN study found that tenofovir recipients were more likely to experience a decline in kidney function. Again, impaired kidney function was linked to older age and high blood pressure (abstract THPE0231).

Taken together, the conflicting results of these studies leave open the question of whether tenofovir raises the risk of kidney toxicity in people with HIV. It does seem clear, however, that kidney dysfunction is uncommon in people taking tenofovir, and mainly occurs in people with pre-existing risk factors.

8/15/08

References

C Castellano, W Williams, TB Kepler, and others. Clinical predictors of tenofovir-associated nephrotoxicity in HIV-1-infected patients. XVII International AIDS Conference (AIDS 2008). Mexico City. August 3-8, 2008. Abstract WEAB0104.

MK Rawlings, J Klein, ET Klingler, and others. Impact of drug therapy and co-morbidities on the development of renal impairment in HIV-infected patients. Results of a large retrospective database study. XVII International AIDS Conference (AIDS 2008). Mexico City. August 3-8, 2008. Abstract THPE0182.

ET Overton, K Mondy, L Conley, and others. Prevalence and predictors of renal insufficiency among HIV-infected patients in the study to understand the natural history of HIV/AIDS in the era of effective therapy. XVII International AIDS Conference (AIDS 2008). Mexico City. August 3-8, 2008. Abstract THPE0231.