Zithromax has been approved for the treatment of Mycobacterium avium complex (MAC) in subjects with advanced HIV infection. Zithromax is taken in a once-weekly 1200 mg dose (two 600 mg tablets).

Clinical trials document that prophylaxis with once-weekly Zithromax reduced the risk of developing MAC bacteria in the bloodstream and the clinical signs and symptoms associated with it.

Two randomized, double-blind trials conducted in people with advanced HIV infection demonstrated that Zithromax effectively reduced the risk of developing disseminated MAC. In one of these pivotal studies, Zithromax was compared to rifabutin and the combination of these two agents. In this large double-blind study, there was a statistically significant difference in favor of Zithromax in the one-year cumulative incidence rate of disseminated MAC. Additionally, Zithromax-rifabutin combination therapy was to be more effective than rifabutin as monotherapy.

Formal drug interaction studies have demonstrated that Zithromax can be used concomitantly with many medications commonly prescribed for subjects with advanced HIV infections, such as zidovudine, didanosine, or rifabutin, without dosage adjustments. Currently, no data are available evaluating the concomitant use of Zithromax and the recently approved protease inhibitors.

Overall side effects in Zithromax-treated subjects were primarily mild to moderate in nature and consisted mainly of diarrhea, nausea, abdominal pain, and loose stools. Gastrointestinal side effects observed in subjects treated with Zithromax were statistically greater than those observed in the rifabutin-treated subjects. There was no statistically significant difference in discontinuations due to side effects among the treatment groups.

Zithromax is contraindicated in subjects with known hypersensitivity to azithromycin, erythromycin, or any macrolide antibiotic.

MAC is the most common systemic bacterial infection in persons with advanced AIDS: MAC has been confirmed post-mortem in more than 50% of persons with advanced HIV infection, and the U.S. Centers for Disease Control and Prevention estimates that one in every four persons living with AIDS has disseminated MAC. Caused by the M avium bacterium, disseminated MAC infection results in symptoms that include fever, night sweats, fatigue, abdominal pain, chronic diarrhea, and weight loss or "wasting."