Seattle Treatment Education Project: STEP Perspective - Volume 4,
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
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
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).
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).