Effectiveness of erythromycin in the treatment of acute bronchitis

Clinical trials have not shown a consistent benefit of treating bronchitis with antibiotics. Many physicians, however, treat acute bronchitis with antibiotics because of the possibility of Mycoplasma pneumoniae or other pathogens. The objectives of this study were to determine the effectiveness of erythromycin treatment in patients with acute bronchitis and to determine whether a newly developed rapid M pneumoniae antibody test is useful in predicting which patients will respond to therapy.

We conducted a randomized, double-blind, placebo-controlled clinical trial at three primary care centers in North Carolina. A convenience sample of 140 patients presenting with acute bronchitis were tested for M pneumoniae, 91 of whom were treated with either erythromycin 250 mg four times daily for 10 days or an identical-appearing placebo.

Patients treated with erythromycin missed an average of only 0.81 +/- 1.1 days of work compared with 2.16 +/- 3.2 days for placebo-treated patients (P < .02). There were no significant differences in cough, use of cough medicine, general feeling of well-being, or chest congestion between the erythromycin and placebo groups. Twenty-five percent of the patients tested positive for M pneumoniae. There were no differences in response to erythromycin based on whether the patient had a positive test for M pneumoniae.

Erythromycin is effective in significantly reducing lost time from work, but it is not effective in reducing cough or other symptoms in patients with acute bronchitis, regardless of the outcome of the M pneumoniae antibody test.