Azithromycin no more effective than vitamin C for acute bronchitis

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Evans AT, Husain S, Durairaj L, et al. Azithromycin for acute bronchitis: a randomised, double-blind, controlled trial. Lancet 2002; 359:1648–54.



BACKGROUND: The results of studies evaluating the effectiveness of antibiotic treatment for acute bronchitis are conflicting, some with uncertain reliability and validity. Although most studies of antibiotics have focused on cure of disease or reduction in symptoms, this study tested whether patients with acute bronchitis who were treated with azithromycin experienced greater improvements in health-related quality of life than those treated with vitamin C. The authors chose to compare azithromycin with vitamin C instead of traditional placebo because they believed potential patients might refuse to participate in the study if there was a chance they would receive a placebo. Evidence has shown that vitamin C at the doses used in this study is ineffective in the treatment of acute bronchitis or other respiratory illnesses, making the vitamin a reasonable placebo for this study.1
POPULATION STUDIED: The authors studied 220 adults with cough lasting 2–14 days who were diagnosed with acute bronchitis after presenting to an ambulatory screening clinic in Chicago, Illinois. Patients were excluded if they had any underlying lung disorder, clinical characteristics of pneumonia, antibiotic treatment within the previous 2 weeks, pregnancy, steroid treatment, or had been started on an angiotensin-converting enzyme inhibitor within the previous 4 weeks.
STUDY DESIGN AND VALIDITY: This study was a randomized, double-blinded, controlled trial with concealed allocation. Patients were randomized to receive a total of 1.5 g of either azithromycin or vitamin C over 5 days (500 mg on the first day, then 250 mg/day for 4 more days). All patients also received symptomatic care with dex-tromethorphan and an albuterol inhaler with a spacer. Trained research assistants interviewed patients on enrollment in the study to assess their baseline health-related quality of life. The interview, consisting of 22 questions adapted from similar instruments developed at McMaster University, was repeated on days 3 and 7. For each of the questions, patients were asked to rate how troubled they had been during the previous few days as a result of their bronchitis symptoms on a 7-point scale. Follow-up was for 7 days from the beginning of the study and was 85.9% complete. Analysis was by intention to treat.
OUTCOMES MEASURED: The primary outcome measured was health-related quality of life on day 7 of follow-up. Secondary end points were return to usual daily activities at follow-up and adverse effects.
RESULTS: The adjusted difference in health-related quality of life between the patients taking azithromycin and those taking vitamin C was not significant on day 7 of the study (difference = 0.03; 95% confidence interval [CI], –0.20 to 0.26). Overall, 89% of patients in both groups returned to work by day 7 (difference = 0.5%; 95% CI, –10% to 9%). No difference was noted in the fre treat acute bronchitis in otherwise healthy adults.


Azithromycin is no more effective than vitamin C in treating acute bronchitis in healthy adults. Given the evidence that treatment with vitamin C is not effective in respiratory illnesses, azithromycin appears equally ineffective. With increasing health care costs and rising concerns about antibiotic resistance, azithromycin, and probably other antibiotics, should not be used to treat acute bronchitis in otherwise healthy adults.

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