Two hundred and forty-six patients infected with human immunodeficiency virus 
(HIV) who also had disseminated Mycobacterium avium complex received either 
azithromycin 250 mg every day, azithromycin 600 mg every day, or clarithromycin 
500 mg twice a day, each combined with ethambutol, for 24 weeks. Samples drawn 
from patients were cultured and clinically assessed every 3 weeks up to week 12, 
then monthly thereafter through week 24 of double-blind therapy and every 3 
months while on open-label therapy through the conclusion of the trial. The 
azithromycin 250 mg arm of the study was dropped after an interim analysis 
showed a lower rate of clearance of bacteremia. At 24 weeks of therapy, the 
likelihood of patients' developing 2 consecutive negative cultures (46% vs. 56%, 
P=.24) or 1 negative culture (59% vs. 61%, P=.80) was similar for azithromycin 
600 mg (n=68) and clarithromycin (n=57), respectively. The likelihood of relapse 
was 39% versus 27% (P=.21) on azithromycin compared with clarithromycin, 
respectively. Of the 6 patients who experienced relapse, none of those 
randomized to receive azithromycin developed isolates resistant to macrolides, 
compared with 2 of 3 patients randomized to receive clarithromycin [corrected]. 
Mortality was similar in patients comprising each arm of the study (69% vs. 63%; 
hazard, 95.1% confidence interval, 1.1 [0.7, 1.7]). Azithromycin 600 mg, when 
given in combination with ethambutol, is an effective agent for the treatment of 
disseminated M. avium disease in patients infected with HIV.