Although the incidence of tuberculosis has decreased in the United States over the last few decades, the incidence of chronic pulmonary infections with nontuberculous mycobacteria (NTM) appears to be increasing. Unfortunately, a common problem in the management of these infections is the inability of elderly patients to tolerate the currently recommended multidrug regimen of (1) azithromycin or clarithromycin, (2) rifampin or rifabutin, and (3) ethambutol. The most frequent adverse reactions of MAC treatment are gastrointestinal (GI), most commonly associated with the macrolides and rifampin. Although macrolide toxicity is generally dose-related, the role of routine monitoring of drug concentrations and subsequent dose adjustment has not been studied. The role of anti-emetics or dietary supplements to mitigate these symptoms is also not defined.