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VIII International Conference on AIDS: Mycobacterium Avium Complex (MAC)
Lori Panther, M.D.
March 10, 1992
Seattle Treatment Education Project: STEP Perspective - Volume 4,

Prophylaxis MAC (also called MAI) infection frequently occurs in HIV-positive people. In contrast to TB it occurs at lower CD4 counts, usually below 100. Significant problems from MAC infection may occur, including fever, sweats, wasting syndrome, and bone marrow depression. Administration of AZT significantly delays the onset of MAC disease as well as improves survival after MAC is diagnosed (Cartledge, UK, PoB3073). Standard of care for MAC is to treat the infection with a combination of drugs with a clinical goal of decreased symptoms. Recently, the question of drug prophylaxis for MAC (in the manner of PCP prophylaxis) has been entertained.

Drug prophylaxis for an opportunistic infection during HIV infection requires that it be well-tolerated, effective, affordable, non-toxic, and have little interaction with other frequently used drugs. More long-term studies would elucidate whether MAC prophylaxis improved survival or quality of life in HIV infection. Another question is whether emergence of resistant MAC to the drugs used in prophylaxis will present a significant clinical problem. Several studies of drug prophylaxis for MAC were presented.

A placebo-controlled study of rifabutin for MAC prophylaxis was discussed. In over 160 people in each group receiving placebo or 300 mg/day of rifabutin, 9.6 percent of those receiving rifabutin developed MAC compared to 23 percent receiving placebo. Rifabutin remains an attractive agent in the prophylaxis of MAC (Cameron, Canada, WeB1055). These data were confirmed by other smaller studies (Gordin, USA, PoB3081).

A study of clofazimine for prophylaxis of MAC was also presented. Although its efficacy could not be determined with confidence from the data presented, it does not look very promising. In individuals receiving 50 mg of clofazimine a day, seven developed MAC versus six who received no treatment (PoB3345).

Treatment Clarithromycin and azithromycin have emerged in the treatment of MAC infection. Current recommendations include the use of clarithromycin, clofazamine and ethambutol in the treatment of MAC, though there have been no adequate studies assessing the utility of adding ethambutol for this regimen (Benson, USA, Session 129). Other options are the use of azithromycin in place of clarithromycin or rifabutin in place of clofazamine in the regimen noted above (Chaisson, USA, Session 136).

A phase II treatment study of clarithromycin as an agent in MAC was presented. Over 100 people on 1, 2 or 4 gm/day of clarithromycin were followed for 12 weeks. The 2 and 4 gm/day dose groups showed a 100 percent response in clearing MAC bacteria from the blood, and significant improvement in fever, sweats, and quality of life. However, there was an overall 22 percent incidence of resistant MAC emerging during therapy. Therefore, combination therapy with a second agent was advised (Chaisson, USA, WeB1052). Several studies presented confirmed this data (PoB3336, PoB3343).