Physicians in the U.S. commonly prescribe the antibiotic azithromycin (Zithromax) for the treatment of acute bronchitis. However, research has not yielded conclusive evidence that azithromycin is effective in treating acute bronchitis. As an antibiotic, azithromycin has the ability to kill bacteria, but most cases of bronchitis are caused by viruses rather than bacteria. This means that whether you take an antibiotic or not, you’ll get better when the illness runs its course, though you can take cough medicine to relieve symptoms in the meantime.

In an article recently published in The Lancet , researchers reported that azithromycin was no more effective than a placebo (inactive) pill in treating acute bronchitis.

About the study

Researchers from Cook County Hospital in Chicago, along with colleagues from the Universities of Pittsburgh and Iowa, studied 220 acute bronchitis patients from the screening clinic at Cook County Hospital. All patients were adults with a cough lasting 2 to 14 days and were diagnosed with acute bronchitis at the clinic between December 1999 and March 2000. Patients were excluded if they had a chronic lung disease, were pregnant, had another infectious disease that required medication, needed to be admitted to the hospital, or showed signs of pneumonia. Patients currently taking the following medications were also excluded: bronchodilators, glucocorticoids, ACE inhibitors (in last 4 weeks), and antibiotics (in last 2 weeks).

Participants were randomly assigned to receive either 250 mg of azithromycin once per day for five days or 250 mg of vitamin C once per day for five days. Vitamin C was used as a placebo because research shows that people won’t participate in this type of study if they might get a dummy pill, but a vitamin pill is considered acceptable. However, there is no evidence that 250 mg of vitamin C is effective in treating acute bronchitis or any other respiratory illness. All participants were also given dextromethorphan cough syrup and an albuterol inhaler for symptomatic relief of coughing.

This study was double-blind, meaning that neither the patients nor the interviewers knew what treatment each patient was receiving.

At the first doctor visit for bronchitis (day 1), participants were interviewed about their health-related quality of life and their activity limitations (such as missed work or reduced physical activity) due to their bronchitis. This interview was repeated by telephone on day 3 and day 7.

The researchers compared the health-related quality of life on day 7 reported by people taking azithromycin with that of people taking the placebo pill. In addition, they compared the time it took to return to normal activities—work, exercise, school, housework, etc.—between the two groups.

The findings

There was no difference in the health-related quality of life reported by the two groups on day 7. In addition, there was no difference between the two groups in the number of days to return to usual activities. These findings indicate that taking azithromycin did not help acute bronchitis patients feel better or resume regular activities sooner than patients taking a placebo.

Although these results are interesting, there are limitations to this study.

The institutional review board stopped this study early, when only 220 people had participated rather than the planned 400 people, because the interim results clearly showed the ineffectiveness of azithromycin. However, this left too few people in the study to examine whether severity of symptoms or patient age affected recovery time—for example, severe versus moderate cough and elderly people versus younger adults. In addition, 17% of participants did not complete the study and were unavailable to be interviewed and included in the analysis. However, the percentage of people lost to follow-up was similar in both groups. Finally, although this study suggests that azithromycin is ineffective in treating chronic bronchitis, it does not identify a better treatment for the condition.

How does this affect you?

Do you need an antibiotic for acute bronchitis? Probably not. The majority of acute bronchitis cases are not caused by bacteria, so an antibiotic won’t help. And the findings of this study suggest that azithromycin, the most commonly prescribed antibiotic for acute bronchitis, is not effective in treating the condition. People who took a dummy pill in this study got better just as quickly as those who took azithromycin.

Taking antibiotics when you do not have a bacterial infection contributes to the development of bacteria that are resistant to antibiotics. The decision to prescribe an antibiotic is up to your health care provider, but you can help by not demanding an antibiotic when your health care provider feels it is unnecessary. And you can tell your health care provider that you do not want an antibiotic unless he or she suspects you have a bacterial infection. If your health care provider has reason to suspect a bacterial infection, he or she may prescribe an antibiotic.