Important note: Information in this article was accurate in October 2000. The state of the art may have changed since the publication date.
The release of two drugs in the 1990s - azithromycin and clarithromycin - has greatly increased the chances for sustained recovery from MAC (Mycobacterium avium complex). Azithromycin (Zithromax) 1200 mg taken once weekly became an accepted prevention or prophylaxis against MAC, and a few other infections.
People taking HAART (Highly Active Antiretroviral Therapy) often have their CD4+ and other cell counts increase. As well, their immune system's ability to detect and fight MAC improves while PHAs take HAART. Doctors are giving some of their patients who respond well to HAART the option of discontinuing anti-MAC medication.
A large American study called ACTG 362 monitored more than 600 PHAs taking HAART, half of whom discontinued taking azithromycin. After about 16 months only two cases of MAC developed in people not taking azithromycin - this is fewer than 1% of subjects. The study doctors state that azithromycin prophylaxis can be "safely" stopped in PHAs whose CD4+ cell counts increase [to at least 100 cells] as a result of anti-HIV therapy.
Researchers recruited 643 subjects (13% female, 87% male) who had at one time a CD4+ count of 50 or fewer cells. Due to use of anti-HIV therapy, the CD4+ counts of subjects had increased to at least 100 cells at the time they entered the study. No subject had been diagnosed with MAC before enrolling in this clinical trial. At the start of the study, subjects had the following basic lab values:
Researchers gave half the group azithromycin 1200 mg per week and the remaining subjects received fake azithromycin (placebo). Subjects continued to take their anti-HIV therapy throughout the study.
After about 16 months the following numbers of subjects in each group developed MAC infection:
The two cases of MAC were unusual because they were not associated with typical symptoms of MAC. Indeed technicians were only able to grow MAC from samples taken from the spines of subjects. Doctors reported that the only symptoms subjects reported were "neurologic". No further details about symptoms were supplied by the doctors. Around the time doctors diagnosed MAC infection, these two subjects had a viral load of fewer than 500 copies and CD4+ counts of 306 and 203 cells.
The following proportion of subjects in each group stopped taking their assigned drug (azithromycin or placebo) because of side effects:
This difference was statistically significant, that is, not likely due to chance alone.
Common complaints from subjects while in the study included the following:
During the study 18 subjects in the following groups developed 19 AIDS-related complications:
This is a very small number of people with such complications given the large size of the study. The researchers were surprised to find that the rate of AIDS-related illnesses was significantly reduced in the azithromycin group. They suggested that more sensitive tests "may be needed to identify the rare patient who remains at risk [for serious infections] despite an increased CD4+ cell count." Nevertheless, the researchers state that their results support recent American recommendations about stopping MAC prophylaxis.
At least two other studies have found that some HIV+ women are at increased risk for developing AIDS-related bacterial infections. Although researchers recruited only 82 women for the present study, about 10% developed "one or more of these infections" as compared to 4% of the men. Researchers remained puzzled as to why this difference occurred.
1. Currier JS, Williams PL, Koletor SL, et al. Discontinuation of Mycobacterium avium complex prophylaxis in patients with antiretroviral therapy-induced increases in CD4+ cell counts: a randomized, double-blind, placebo-controlled trial. Ann Intern Med 2000 Oct 3;133(7):493-503.
2.Havlir DV, Schrier RD, Torriani FJ, et al. Effect of potent antiretroviral therapy on immune responses to Mycobacterium avium in human immunodeficiency virus-infected subjects. J Infect Dis 2000 Dec;182(6):1658-63.
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