HIV-positive people taking Sustiva® (efavirenz) may be able to lower their levels of bad cholesterol by switching to Viramune® (nevirapine), according to the results of a small study published in the July 15 issue of Clinical Infectious Diseases.

The Switch of Non-nucleoside Reverse Transcriptase Inhibitors to Reduce the Occurrence of Cardiovascular Complications (SIROCCO) study found that, after 52 weeks of follow up, dropping Sustiva for Viramune led to a moderate drop in blood levels of low-density lipoprotein (LDL), the form of cholesterol that can cause arterial blockage (atherosclerosis).

According to the study authors, led by Jean-Jacques Parienti, MD, of the Université Pierre et Marie Curie in Paris, the switch effectively reduced the risk of a heart attack or stroke. In addition, patients who switched to Viramune did not experience signs or symptoms of major drug toxicity.

Previous studies have suggested that, compared to the results of clinical trials evaluating the safety of Sustiva, Viramune is less likely to cause LDL cholesterol increases. And while numerous studies have evaluated the benefits of switching patients from a cholesterol-raising protease inhibitor to a non-nucleoside reverse transcriptase inhibitor (NNRTI), none have looked at the effects of switching from one NNRTI to another with respect to changes in blood fats.

SIROCCO is the first trial to evaluate the benefits of switching patients with high LDL levels from Sustiva to Viramune.

The French study enrolled 37 patients and was conducted from June 2003 to February 2006. The patients selected all had viral loads below 400 after being on a Sustiva-based regimen for at least six months. Patients were also required to have very high LDL cholesterol levels (above 132 mg/dL).

The patients were split into two groups – one remained on Sustiva and the other group switched to Viramune (200 mg twice daily). In addition to monitoring LDL levels, the researchers closely monitored patients for rash and elevated liver enzymes, two potentially serious reactions that can occur in people starting Viramune with relatively high CD4 cell counts.

At the time they entered the study, patients had been on Sustiva for approximately 41 months and had an average CD4 cell count of 530. LDL levels upon entering the study averaged 165 mg/dL (4.22 mmol/L).

After a year in the study, viral loads remained below 400 in all patients. CD4 counts increased by an average of 34 cells among those who remained on Sustiva, compared to an average decrease of 8 cells among those who switched to Viramune. This difference, however, was not statistically significant, meaning that it could have been due to chance.

LDL cholesterol levels decrease by 17 mg/dL in the Viramune group after 52 weeks, compared to a 4 mg/dL decrease among those who remained on Sustiva. Compared to their pre-switch LDL levels, the average decrease among those in the Viramune group was statistically significant. While technically only a moderate drop in LDL among those who switched, Dr. Parienti's group writes that the "decrease corresponds to a 20% decrease in the 10-year relative risk for major cardiac events."

Of interest, LDL cholesterol levels dropped the most in patients with the highest blood concentrations of Viramune, measured using therapeutic drug monitoring.

Dr. Parienti's team also notes that while there may be long-term benefits associated with a switch to Viramune, they should be balanced against the potential for serious liver problems and rash among people who start or switch to the drug with a high CD4 cell count (250 or higher in women and 400 or higher in men). However, at least in this study, there were no reports of severe skin problems or spikes in liver enzymes after the Sustiva-to-Viramune switch.

"It is unknown whether the switching from [Sustiva] to [Viramune] when CD4 cell counts are above these thresholds is associated with the same risk as starting [therapy] with [nevirapine]," the authors write. Previous studies have not found an increased risk of liver or skin reactions among patients switching to Viramune from Sustiva, regardless of the CD4 count at the time of the switch.

The authors conclude that switching from Sustiva to Viramune therapy was associated with significant reductions in LDL cholesterol after 52 weeks. However, additional studies "are needed to assess the role of these drugs on the incidence of [cardiovascular problems] in large cohorts of patients with HIV infection."