Mycobacterium avium Complex (MAC)

November 2004 View PDF En español

Treatments

Treatment reduces the symptoms of MAC disease and improves your quality of life. However, treating MAC is difficult for several reasons:

MAC can easily become drug-resistant.
MAC strains found in people with HIV are naturally more drug-resistant than those found in most HIV-negative people. Treatment usually involves taking several drugs for a long time. Combining several drugs increases the chance of side effects and drug interactions and can be expensive. This may mean that people do not finish the full treatment, which can lead to drug resistance.
The needed dose of drug may cause serious side effects.
Some drugs used to treat MAC are destroyed by stomach juices or cannot be dissolved in body fluids. It is particularly difficult for drugs to get into cells called macrophages, where MAC bacteria are found. In order to have high enough levels of the drug at the site of infection, higher doses may be needed. This may then lead to side effects.
The effect of a drug on MAC bacteria in a lab test is not a reliable guide to treating someone with MAC.
Resistance patterns of MAC bacteria vary a lot. It may be difficult to work out the best MAC treatment for an individual.

Treating MAC infection requires several drugs because no one drug by itself is effective. MAC bacteria can quickly become resistant to a drug and to other drugs in the same family. Combination therapy is more effective and may slow the development of drug resistance.

The Public Health Service Task Force
recommends that MAC treatment includes:
clarithromycin (Biaxin; 500mg twice a day) or
azithromycin (Zithromax; 500–600mg/day)
PLUS
ethambutol (Myambutol; 15mg/kg/day)
PLUS one or more of
rifabutin (Mycobutin), rifampin (Rifadin, Rimactane),
ciprofloxacin (Cipro) or amikacin (Amikin)

Use of clofazimine (Lamprene) has been shown to increase the risk of death during MAC treatment in several studies, so it should not be used.

Azithromycin and clarithromycin are related antibiotics. They are approved for treating serious bacterial infections including MAC in combination with at least one other drug. Resistance to clarithromycin develops quickly when used alone. The higher the level of bacteria in the blood before starting therapy, the more rapid resistance develops.

Clarithromycin has been studied together with various anti-MAC therapies. Studies show that a combination of clarithromycin, ethambutol and rifabutin may prevent developing resistance to clarithromycin, which is common with two-drug combinations. One study also showed that people using the three drugs had fewer symptoms and lower levels of MAC bacteria in their blood. Survival was also longer on three-drug regimens.

This suggests that using clarithromycin or azithromycin together with ethambutol and rifabutin should now be the standard treatment for people with MAC disease. However, several studies have shown that people taking 1,000mg of clarithromycin twice a day had a higher death rate than those taking 500mg twice a day. The higher dose should not be used.

Doctors have had less experience with azithromycin for treating MAC compared to clarithromycin. Studies are underway to find the best treatment combination using azithromycin.

Several pharmaceutical companies have payment assistance programs for their anti-MAC drugs. Doctors should call the toll-free number:

Azithromycin: Pfizer, Inc., 1-800-869-9979
Clarithromycin: Abbott Laboratories, 1-800-688-9118
Ethambutol: Dura Pharmaceuticals, 1-800-859-8586
Rifabutin: Pharmacia, 1-800-242-7014

Diagnosis

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