Adding a fourth drug to an anti-retroviral regimen for the initial treatment of HIV-1 did not lead to significant differences in reducing virus levels in the blood, according to a U.S. study released on Sunday.

The findings were published in the Aug. 16 edition of the Journal of the American Medical Association. The researchers from the Medical College of Cornell University also presented their study at the International AIDS Conference in Toronto, Canada.

"We found no significant differences over three years between the standard 3-drug regimen ... and the 4-drug regimen ... for the initial treatment of HIV-1 infection," wrote the researchers led by Dr. Roy Gulick.

"High rates of virologic suppression achieved in this study support current guidelines that recommend two nucleosides plus efavirenz among preferred regiments for the initial treatment of HIV-1 infection," they added

"Adding abacavir as a fourth drug to the standard initial 3-drug regimen did not change toxicity or adherence but provided no additional benefit," the researchers concluded.

The current standard of care for initial treatment of HIV-1 infection is a three-drug anti-retroviral regimen, also known as the "cocktail" that can suppress presence of HIV in the blood, increase CD4 immune cells, delay clinical progression and improve survival.

Some researchers have suggested that adding drugs to the 3-drug regimens could improve anti-retroviral activity. But after a three-year clinical trial on 765 HIV-1 patients, the Cornell researchers found that the 4-drug regimen might also cause virologic failure, adverse events or drug resistance.

Additional drugs may also increase complexity, the potential for toxicity and costs, said the researchers.

In this study, the participants received either a 3-drug cocktail of zidovudine, lamivudine and efavirenz or a 4-drug regimen of zidovudine, lamivudine, abacavir and efavirenz.

Overall, 26 percent of the 382 patients receiving the 3-drug cocktail and 25 percent of 383 receiving the 4-drug regimen witnessed protocol-defined virologic failure. And the difference of time for first virologic failure was not significant between the two treatment groups.

Source: Xinhua