From the Guidelines
For symptomatic MAC infection in an older, non-immunocompromised adult with cough, the recommended treatment is a three-drug regimen consisting of a macrolide, ethambutol, and rifampin. The most effective regimen is:
- Clarithromycin 500 mg twice daily or Azithromycin 250-500 mg daily
- Ethambutol 15 mg/kg daily
- Rifampin 450-600 mg daily This regimen should be continued for at least 12 months after achieving negative sputum cultures, with a typical treatment duration of 18-24 months total 1.
Additional considerations for treatment include:
- Monitoring visual acuity and color vision monthly due to ethambutol's potential ocular toxicity 1
- Performing baseline and periodic liver function tests to assess for potential hepatotoxicity associated with clarithromycin, azithromycin, rifabutin, and rifampin 1
- Adjusting dosages for renal impairment if necessary, as many of these medications are renally cleared 1
- Ensuring adequate vitamin D levels to support immune function, although the specific impact of vitamin D on MAC treatment outcomes is not well-defined in the provided evidence
The chosen regimen is based on the most recent and highest quality evidence available, which emphasizes the importance of multidrug therapy for MAC lung disease to reduce the risk of drug resistance and improve treatment outcomes 1. The macrolide (clarithromycin or azithromycin) serves as the cornerstone of therapy, while ethambutol and rifampin provide synergistic effects. Long-term treatment is necessary due to the slow-growing nature of MAC organisms and to prevent relapse.
It is crucial to monitor patients for toxicity, given the number of drugs and the older age of these patients, including monitoring for ethambutol ocular toxicity, liver enzymes, auditory and vestibular function, renal function, and leukocyte and platelet counts 1. Patients who receive both clarithromycin and rifabutin must be monitored for the development of toxicity related to the interaction of these drugs 1.
From the FDA Drug Label
When rifabutin is used concomitantly with clarithromycin for MAC treatment, a decreased dose of rifabutin is recommended due to the increase in plasma concentrations of rifabutin The treatment for symptomatic Mycobacterium Avium Complex (MAC) infection presenting with cough in an older adult who is not immunocompromised is clarithromycin with rifabutin. The dose of rifabutin should be decreased when used concomitantly with clarithromycin due to increased plasma concentrations of rifabutin 2.
From the Research
Treatment for Symptomatic Mycobacterium Avium Complex (MAC) Infection
- The treatment for symptomatic Mycobacterium Avium Complex (MAC) infection presenting with cough in an older adult who is not immunocompromised typically involves multidrug regimens including macrolides 3.
- Guidelines-based MAC therapy with multidrug regimens including macrolides is usually effective, but the effectiveness of these regimens can vary 3.
- Azithromycin, clarithromycin, rifabutin, ciprofloxacin, ethambutol, clofazimine, and amikacin have all been suggested for use in treating MAC bacteremia, but the most active combinations of these drugs have not been identified 4.
Treatment Regimens
- Intermittent azithromycin and ethambutol therapy may be an optional treatment regimen for noncavitary MAC-PD, with 76% of patients achieving sputum culture conversion after 12 months of treatment 5.
- Daily therapy with azithromycin for cavitary MAC-LD and intermittent therapy for noncavitary MAC-LD are recommended, but the effectiveness of these regimens has not been thoroughly investigated 6.
- A study found that 74% of patients enrolled in a regimen of TIW azithromycin, daily ethambutol, daily rifabutin, and initial BIW streptomycin had sputum samples become culture-negative after 6 months of therapy 7.
Factors Affecting Treatment Response
- Peak plasma concentration of azithromycin was associated with favorable microbiological responses in MAC-LD patients receiving a daily regimen, but not an intermittent regimen 6.
- Sputum smear positivity was an independent factor for failure to achieve culture conversion in patients with noncavitary MAC-PD 5.