Long-term, low-dose erythromycin monotherapy for Mycobacterium avium complex lung disease: a propensity score analysis.

Multidrug regimens are initially withheld in mild cases of pulmonary Mycobacterium avium complex (MAC) disease. Based on the anti-inflammatory effects of macrolides, some patients are treated with erythromycin, which does not appear to exhibit cross-resistance with clarithromycin in MAC. The aim of this study was to evaluate the effects and adverse events of erythromycin monotherapy in patients with pulmonary MAC disease. This was a retrospective propensity score analysis consisting of 31 patients treated with erythromycin alone and 72 patients on conservative therapy, all of whom met the ATS/IDSA criteria for pulmonary MAC disease. The primary outcome was exacerbation requiring administration of a multidrug regimen. The secondary outcome was the rate of response to the multidrug regimens after exacerbation as a surrogate variable for cross-resistance to clarithromycin. As a result, erythromycin monotherapy was found to be likely to suppress exacerbation throughout the 7-year observation period after the diagnosis of pulmonary MAC disease (P=0.045, Breslow test). Multivariate analysis showed that erythromycin tended to prevent exacerbation, albeit statistically insignificantly (hazard ratio=0.495, 95% confidence interval 0.198-1.235; P=0.132). In addition, the rate of response to the multidrug regimens after exacerbation in the erythromycin group (56%; 5/9) was similar to that observed in the control group (62%; 13/21) (P=0.528). Erythromycin monotherapy for patients with pulmonary MAC disease may have the potential to suppress exacerbation without inducing cross-resistance to clarithromycin. However, further prospective studies are needed to microbiologically verify the effectiveness and potential for cross-resistance of these drugs.