Alternative Regimens for the Prophylaxis of Mycobacterium avium Complex in Acquired Immune Deficiency Syndrome (AIDS)

Azithromycin, clarithromycin, and rifabutin are all FDA-approved for prophylaxis against Mycobacterium avium complex (MAC) in patients with advanced HIV infection. Recently, results of two large, randomized, controlled trials were reported that may alter the way these compounds are used in preventing MAC. Results have shown that both azithromycin (1,200 mg once weekly) and clarithromycin (500 mg twice daily) are more efficacious than rifabutin in preventing MAC. Combination prophylaxis with a macrolide and rifabutin improves the efficacy of azithromycin but not that of clarithromycin. Additionally, combination therapy has been associated with increased toxicity, resulting in more adverse events. While both azithromycin and clarithromycin are very effective, the once-weekly administration and fewer drug interactions offer an advantage to azithromycin prophylaxis over clarithromycin in most settings.