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Being Alive
MEDICAL UPDATE: Update on MAC Prophylaxis
Mark Katz, MD and reported by Jim Stoecker
August 5, 1993
Being Alive 1993 Aug 5: 5

Last December, the FDA approved Rifabutin as a prophylactic drug for MAC. At the time of approval, we noted that this drug does not function as Bactrim/Septra does for PCP. Rifabutin does not reduce MAC incidence to near zero. Rather, studies indicated that use of Rifabutin could potentially halve the incidence of MAC.

Since the start of the year, many physicians have routinely prescribed Rifabutin for their patients whose CD4 falls below 100. The standard prophylactic dosage is two 150 mg pills per day. Despite the standard use of the drug, however, we are seeing some breakthrough cases of MAC.

These breakthroughs do not necessarily mean that Rifabutin is bad prophylaxis; it may just not be enough. Some researchers believe that Rifabutin is not prophylaxis; rather, it is treatment for early MAC infection. By the time CD4 falls below 100, a person may already be harboring small amounts of MAC colonization. And with such a virulent infection, one drug may not be enough to hold it in check.

Now ACTG 196 will study MAC prophylaxis. This study will look at rifabutin vs. clarithromycin vs. a combination of these two drugs. It may be that the two drugs together will better prevent MAC than the one drug approach. UCLA is one of the local sites for ACTG 196 and you can get more information by calling 310.206.6414 or 800.TRIALS-A.