About The Study

This trial assessed the safety and benefit of rifabutin in preventing or delaying the onset of MAC bacteria in people with AIDS, and examined whether rifabutin prolongs life expectancy.

Study Approach

This was a phase III study, which measures how well a drug works in large groups of people, and was double-blinded (neither doctors nor volunteers knew which therapy volunteers received). Two identical trials were conducted at the same time. In the first trial, 292 patients were randomly assigned to receive rifabutin (300 mg), and 298 to receive placebo. In the second trial, 274 patients were randomly assigned to receive the rifabutin and 282 to receive placebo. The primary endpoint of the study was elimination of MAC bacteremia. The secondary endpoints were symptoms of MAC infection, side effects, hospitalization and survival.

Study population

A total of 1146 participants were randomized. All participants had AIDS, and CD4 cell counts of 200 or less.


In the first trial, MAC bacteremia developed in 51 of 298 participants assigned to placebo (17%) and 24 of 292 participants assigned to rifabutin (8%). In the second trial, bacteremia developed in 51 of 282 patients in the placebo group (18%) and 24 of 274 patients in the rifabutin group (9%). Rifabutin significantly delayed fatigue, fever and hospitalization. The number of adverse events (side effects) was similar with both rifabutin and placebo. Overall survival did not differ significantly between the two groups, although there were fewer deaths with rifabutin (33) than with placebo (47) during the double-blind phase. Adverse events were only marginally higher with the active drug.


Rifabutin, given to prevent MAC, reduces the frequency of MAC infection in patients with AIDS and CD4 counts of 200 of less.