A Study of Azithromycin in the Prevention of Mycobacterium Avium Complex Disease (MAC) in HIV-Infected Patients

Inclusion Criteria Concurrent Medication: Required: * Anti-pneumocystis prophylactic therapy (dihydropteroate synthetase inhibitors with or without dihydrofolate reductase inhibitors, pentamidine). Allowed: * Concomitant anti-HIV therapy (AZT, ddI, ddC) or antifungal therapy (including azoles). Patients must have: * HIV infection. * CD4 count \< 100 cells/mm3. * No MAC positive blood cultures within 1 month prior to study entry. * No symptoms suggestive of disseminated MAC infection (including unexplained diarrhea, fever, and night sweats) within 1 month of study entry. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Positive PPD within 3 months prior to study entry (negative PPD defined as \< 5 mm induration). * Chest x-ray suggestive of any active disease, in particular tuberculosis. * Known hypersensitivity to macrolide antibiotics. * Any other acute clinical condition likely to interfere with completion of the protocol. * Inability to care for self without considerable assistance and medical care. Concurrent Medication: Excluded: * Other investigational new drugs (except for foscarnet or ddC) unless prior agreement has been reached between the investigator and the Pfizer project physician. * Concomitant putative immunostimulants. Patients with the following prior conditions are excluded: History of MAC or Mycobacterium tuberculosis (MTb) infection. Prior Medication: Excluded within the past 4 weeks: * Any putative anti-MAC therapies including rifampin, rifabutin, clofazimine, ethambutol, cycloserine, ethionamide, amikacin, and ciprofloxacin or other quinolones thought to be active against MAC.