To compare the efficacy of clarithromycin/ethambutol with placebo or with rifabutin at two different doses in reducing colony-forming units (CFUs) by 2 or more logarithms in patients with Mycobacterium avium Complex bacteremia and maintaining this response until 16 weeks post-randomization. To assess survival and comparative tolerability among the three treatment regimens.

Patients are randomized to receive clarithromycin and ethambutol plus either placebo or rifabutin at one of two doses. Treatment continues indefinitely. AS PER AMENDMENT 04/19/94: Doses of rifabutin have been lowered.

Inclusion Criteria

Concurrent Medication:

Allowed:

• Isoniazid for TB prophylaxis ONLY.

Patients must have:

• HIV infection.
• MAC infection.
• Life expectancy of at least 16 weeks.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Perceived unreliability or unavailability for frequent monitoring.

Concurrent Medication:

Excluded:

• Antimycobacterial drugs other than the study drugs.
• Carbamazepine.
• Terfenadine.
• Theophylline.

Patients with the following prior condition are excluded:

History of hypersensitivity to rifabutin, rifampin, erythromycin, clarithromycin, azithromycin, or ethambutol.

Prior Medication:

Excluded within 7 days prior to study entry:

• Rifabutin.
• Rifampin.
• Ethionamide.
• Cycloserine.
• Clofazimine.
• Ethambutol.
• Amikacin.
• Ciprofloxacin.
• Ofloxacin.
• Sparfloxacin.
• Azithromycin.
• Clarithromycin.
• Pyrazinamide.

Excluded within 14 days prior to study entry:

• Carbamazepine.
• Terfenadine.
• Theophylline.