The protease inhibitor (PI) ritonavir (Norvir) is often used together with another protease inhibitor such as amprenavir (Agenerase), indinavir (Crixivan) or saquinavir (Fortovase) because ritonavir can boost the level of these other PIs to a higher level than they would ever reach if they were taken without ritonavir. A ritonavir-boosted regimen often has the advantage of better anti-HIV activity than a single-PI regimen. Boosted regimens also allow PHAs to take their pills twice daily rather than three times daily. Another advantage of boosted regimens is that they often involve fewer pills than do unboosted regimens.
Unfortunately, a side effect of ritonavir and other PIs is that levels of certain lipids — cholesterol and triglycerides — usually rise above normal levels in people who use these drugs. Over time, if this increase continues, the risk of developing cardiovascular disease and diabetes increases. One possible way of dealing with this issue is to substitute the non-nuke delavirdine (Rescriptor) for ritonavir in PI-boosted regimens. This may be possible because delaviridine can also boost PI levels.
Doctors in Chicago, Illinois, reviewed medical records of eight male subjects who had initially used ritonavir either by itself or to boost levels of another PI — saquinavir, nelfinavir (Viracept) or indinavir. All subjects later switched their ritonavir for delavirdine-boosted regimens, using that non-nuke to raise levels of PIs.
The doctors found that when subjects switched to a delavirdine-boosted regimen, their lipid levels fell, on average, by about 50%.
Although these findings are encouraging, before there's any rush to dump ritonavir, further study is needed to do the following:
REFERENCE
Schutz M and Nangah S. A comparison of lipid levels on ritonavir- or delavirdine-containing highly active antiretroviral therapy. Abstract 113 - 3rd International Workshop on Adverse Drug Reactions and Lipodystrophy in HIV, 23-26 October 2001, Athens, Greece.
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