Washington, May 15 (ANI): One of the most commonly prescribed triple-drug combinations for initial HIV infection is also the most effective at suppressing it, according to the largest study of its kind to evaluate commonly used HIV drugs.

Researchers at the University of Pittsburgh School of Medicine also found that a two-drug regimen performed comparably to the triple-drug regimens.

The study looked at one of the first class of HIV drugs approved by the U.S. Food and Drug Administration called nucleoside reverse transcriptase inhibitors (NRTIs) and a two-drug regimen that did not include NRTIs.

Although effective and commonly prescribed, NRTIs can produce severe side effects in some patients.

The study, which included 753 participants at 55 centers, found that the popular three-drug combination of efavirenz plus NRTI therapy was more effective at achieving and maintaining reduction of the virus than another commonly prescribed drug combination of lopinavir-ritonavir plus NRTI.

Interestingly, a two-drug combination of lopinavir-ritonavir plus efavirenz had a similar level of effectiveness as each of the triple-drug regimens that contained NRTIs.

HIV levels in 24 percent of the participants in the efavirenz group returned to detectable levels during the almost two-year study compared to 33 percent of participants in the lopinavir-ritonavir group and 27 percent of those in the NRTI-sparing group. All three treatment regimens produced substantial improvements in immune responses.

"Although all three regimens were well-tolerated and effective, our results showed that efavirenz with NRTIs should still be considered the gold standard regimen for initial HIV treatment," said Sharon Riddler, M.D., M.P.H., lead author of the study and associate professor of medicine in the division of infectious diseases at the University of Pittsburgh School of Medicine.

"The results from the NRTI-sparing regimen have given us valuable reassurance that we can utilize a two-drug therapy regimen based on lopinavir-ritonavir plus efavirenz for patients who are unable to take NRTI due to side effects."

"This study not only establishes the best initial therapy for HIV infection, it opens the way toward simpler regimens that contain fewer drugs," said John Mellors, M.D., senior co-author and professor, University of Pittsburgh School of Medicine and University of Pittsburgh Graduate School of Public Health.

The study appears in the May 15 issue of New England Journal of Medicine. (ANI)