The protease inhibitor Reyataz (atazanavir) negatively affects the normal functioning of blood vessels, as has been seen with other protease inhibitors, according to a study published in the May 2009 issue of Heart. The authors suggest that Reyataz reduces the ability of arteries to widen (dilate), a sign of cardiovascular disease (CVD) tied to plaque buildup in the blood vessels.

Reyataz has gained favor among many physicians because it is the protease inhibitor least likely to cause unhealthy changes in cholesterol and triglycerides, which in turn can lead to heart disease. More recently, however, factors other than cholesterol have been fingered as possible CVD culprits in people living with HIV, including impaired blood vessel functioning.

Andreas Flammer, MD, from the University Hospital Zurich in Switzerland and his colleagues focused on one measure of blood vessel health, called flow-mediated dilation (FMD), in people taking Reyataz and other protease inhibitors. When blood vessels are functioning properly, they widen, or dilate,  when blood flows more heavily through them. Among other things, this helps keep blood pressure roughly equal in all parts of the body and ensures a regular supply of oxygen to the brain and the limbs. Researchers in the past decade found that people whose blood vessels have a reduced ability to dilate are more likely to have heart problems.

Flammer and his colleagues randomized 39 HIV-positive people taking a protease inhibitor other than Reyataz to either continue with their regimen unaltered or to switch to Reyataz. Of note, those taking Reyataz did not use low-dose Norvir—a protease inhibitor that has been tied to a higher CVD risk in HIV-positive people.

Flammer’s team measured the impact of the switch on FMD. They found that FMD negatively decreased in both groups to an almost identical degree, despite the fact that people who switched to Reyataz had improvements in cholesterol and triglycerides.

The authors concluded that reductions in FMD might have a negative impact on blood vessels and ultimately the heart. Further research is needed to confirm this finding and determine what, if any, effect Reyataz may have on blood vessel function and heart disease risk.