People who took Viread (tenofovir) with a Norvir (ritonavir)-boosted protease inhibitor (PI) had greater declines in kidney function than people taking Viread with a non-nucleoside reverse transcriptase inhibitor (NNRTI), or people taking a regimen without Viread, say researchers of a new study published in the January 1 issue of the Journal of Infectious Diseases.
Some studies have found that Norvir-boosted PIs elevate blood levels of Viread, a drug that can affect kidney function in a small proportion of people. To determine whether regimens containing both Norvir and Viread are associated with a higher risk of kidney problems, Miguel Goicoechea, MD, of the University of California, San Diego, and his colleagues compared the kidney-related safety of different treatment regimens in the 146-patient California Collaborative Treatment Group (CCTG) Study 578.
Fifty-one people received a three-drug regimen containing a boosted PI plus Viread for 48 weeks. Twenty-nine received a three-drug regimen containing an NNRTI plus Viread, and 66 people received a three-drug regimen that contained either a boosted PI or an NNRTI, but not Viread. Kidney function was determined by measuring creatinine clearance in blood, and blood levels of Viread were checked after two weeks of therapy.
By the end of the study, people who received a regimen containing both a boosted PI and Viread had significantly greater decreases in creatinine clearance—a sign of declining kidney health—than people who received either a regimen containing a NNRTI plus Viread, or those who received a regimen that did not contain Viread. The reason for the higher rates of kidney problems among patients on drug regimens containing a Norvir-boosted PI and Viread wasn’t clear—blood levels of Viread, checked two weeks after starting treatment, were not significantly altered in any of the study groups.
