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For acute bronchitis, antibiotics can reduce cough by about half a day but can cause side-effects

Smith SM, Fahey T, Smucny J, et al. Antibiotics for acute bronchitis. Cochrane Database Syst Rev. 2014;3:CD000245.

Review questions

In people with acute bronchitis, do antibiotics improve symptoms? Are there side-effects?


Acute bronchitis, or acute cough, can last for up to 8 weeks. It is usually caused by a virus; sometimes it can be caused by bacteria.

Antibiotics are often prescribed for acute bronchitis, but they won’t work if the bronchitis is caused by a virus. Antibiotics can have side-effects, sometimes serious. Taking antibiotics also increases antibiotic resistance, which means that antibiotics may not work as well in the future.

How the review was done

The researchers did a systematic review, searching for studies available up to January 2014. They found 17 randomized controlled trials with 3936 people, including children, adolescents, and adults.

The key features of the trials were:

  • people had acute bronchitis, but not pneumonia or tuberculosis, and had been sick for less than 30 days;
  • treatments were antibiotics, including deoxycycline, erythromycin, trimethoprim/sulfamethoxazole, azithromycin, cefuroxime, amoxicillin and co-amoxiclav; and
  • treatments were compared with placebo or no treatment.

What the researchers found

The quality of evidence was generally good.

Compared with placebo or control, antibiotics:

  • reduced the likelihood of having a cough at 2 to 14 days from 50% to 33%—this means that about 17 fewer people out of 100 had a cough at 2 to 14 days;
  • reduced the likelihood of having a night cough at 2 to 14 days from 45% to 30%—this means that about 15 fewer people out of 100 had a night cough at 2 to 14 days;
  • reduced the number of hours of cough by 11 hours, although the difference could be as little as 1 hour to as much as 21 hours;
  • reduced the number of hours of feeling ill by 15 hours, although the difference could be as little as 3 hours to as much as 28 hours;
  • did not increase clinical improvement (having no limitations or being cured or being improved overall); and
  • increased side-effects by from 19% to 23%—this means that about 4 more people out of 100 had side-effects (nausea, vomiting, and diarrhea).


In people with acute bronchitis, antibiotics reduce duration of cough and feelings of illness by half a day. They do not increase overall clinical improvement. Side-effects such as nausea, vomiting, and diarrhea are increased.

Antibiotics vs placebo or no treatment in people with acute bronchitis


Number of trials (people)

Rate of events with antibiotics

Rate of events with placebo or no treatment

Absolute effect of antibiotics at 2 to 14 days

Number of people with cough

4 trials (275 people)



About 17 fewer people out of 100 had a cough

Number of people with night cough

4 trials (538 people)



About 15 fewer people out of 100 had a night cough

Clinical improvement (having no limitations or being cured or being improved overall)

11 trials (3,841 people)



No effect*


12 trials (3,496 people)



About 4 more people out of 100 had side-effects

*Although the rates for the 2 groups look a little different, the differences were not statistically significant. This means that the differences could simply be due to chance rather than due to the different treatments.


A harmless, inactive, and simulated treatment.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Systematic review
A comprehensive evaluation of the available research evidence on a particular topic.

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