The focus of the present study was to determine if adding tenofovir double-dose (600 mg/day) could improve the virologic efficacy of a failing combined antiretroviral regimen in patients with NRTI-resistant HIV, lead author Dr. Stephanie Dominguez, from CHU Pitie-Salpetriere in Paris, and colleagues note.

The pilot, open-label study involved 10 patients who were treated with double-dose tenofovir for 4 weeks in addition to their failing regimen. The median viral load and CD4 cell count at baseline were 3.66 log10 copies/mL and 407 cells/microliter, respectively.

The new findings appear in the Journal of Medical Virology for February.

By the end of the study, four patients had experienced a drop in viral load of at least 0.8 log10, which was maintained for up to 24 weeks, the report indicates. The median reduction in viral load was -0.61 log10 and the median increase in CD4+ cell count was 109 cells/microliter.

Treatment with tenofovir at the specified dose increased plasma levels of the drug twofold, but except for one patient who developed de Fanconi syndrome at week 2, no serious drug-related side effects were seen.

"This add-on pilot study supports the concept of double dose tenofovir to overcome virologically the decreased sensitivity of NRTI-resistant viruses," the authors state. "However, given the uncertainty regarding renal long-term tolerance of such a regimen, this regimen needs to be considered carefully within a controlled, clinical trial in salvage therapy."

J Med Virol 2007;79:105-110.

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