To evaluate the efficacy and safety of azithromycin administered once a week in the prevention of disseminated Mycobacterium avium complex (MAC) in severely immunocompromised HIV-infected patients with a CD4 count < 100 cells/mm3.

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.