Fewer drugs, same outcome: simpler HIV regimens are effective.

The current standard of HIV treatment isn't improved by the addition of a fourth drug, a 3-year study concludes. Moreover, after their disease is under control, some patients can maintain health by taking only a single drug, according to a smaller, shorter study.

To keep HIV from replicating, clinicians have over a decade or so changed standard patient therapy from a one-drug regimen to two medications and then to three. Each drug attacks the virus in a different way. Some physicians have argued that adding a fourth drug is the next step, but four-drug clinical trials have been inconclusive.

Now, Roy M. Gulick of Weill Medical College in New York City reports "definitive results" that the four drugs he tested work no better than three. Beginning in 2001, his research team issued the current standard therapy to 382 patients with H IV and a four-drug therapy to 383 others. The fourth drug tested was one of several that counter HIV differently than drugs in the standard therapy do.

At the start of the trial, the patients averaged more than 72,000 copies of the virus in each milliliter of blood. After 3 years, 85 percent of the group getting three drugs had viral counts below 50 copies/ml, which is the lowest concentration that the researchers could detect. By comparison, 88 percent of patients taking the four-drug treatment reached that minimum.

In viral counts and other characteristics measured, there was no significant difference between the treatments, the researchers report in the Aug. 16 Journal of the American Medical Association (JAMA).

"Any way you looked at it, four drugs was not an added benefit over the three drugs we have today," Gulick says.

The findings show that there's no reason to deviate from standard treatment, says AIDS specialist Joel E. Gallant of Johns Hopkins University in Baltimore. "The way we're going right now is the right way to go," he says.

Nevertheless, even the three-drug treatment is costly and inconvenient, says Susan Swindells of the University of Nebraska Medical Center in Omaha. Moreover, the standard regimen limits a patient's backup options if the treatment loses effectiveness.

For those reasons, Swindells led a preliminary study to see whether a single drug could maintain control of HIV after a multiple-drug regimen has suppressed the virus. Swindells' team enlisted 34 patients whose viral counts had stayed below 50 copies/ml during the previous year. The patients then received only a single drug.

Six months later, 31 of the patients didn't exceed their original counts in 2 consecutive weeks.

However, three patients surpassed that count in two consecutive weekly tests. At least two of these patients hadn't taken all their medication, the team reports.

Some scientists had feared that single-drug therapy would permit HIV to mutate into a strain resistant to the drug, but that didn't happen in these patients over the 6-month period, Swindells says.

Swindells and her team report their results in the Aug. 16 JAMA.

Single-drug regimens might contribute greatly in countries with limited treatment resources, says AIDS clinician Robert T. Schooley of the University of California, San Diego. In the end, he says, each patient will require a different balance between fighting HIV with the most drugs available and using the simplest effective treatment.