In Summary, for those who received the antibiotics:

Benefits in NNT

  • 100% saw no benefit
  • 18% were helped by a reduction in symptoms, including cough
  • None were helped (overall)
  • 1 in 6 were helped (no cough at follow up)

Harms in NNT

  • 2.6% were harmed by medication side effects
  • 1 in 37 were harmed (minor adverse effects at follow up)

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Source: Smith SM, et al. Antibiotics for acute bronchitis. Cochrane Database of Systematic Reviews 2004, Issue 4

Efficacy Endpoints: Clinical improvement or cure

Harm Endpoints: Reduction in cough

Narrative: Acute bronchitis is defined as a cough-related illness lasting 1-3 weeks with or without sputum in an individual without chronic lung disease and a normal chest radiograph.1 It is one of the most common conditions for which patients consult a physician and the most common reasons for seeking care are symptom severity, duration, and interference with daily activities.2 Less than 10% of cases are thought to be bacterial, few patients cite needing an antibiotic, and most guidelines do not recommend their routine use in bronchitis.1 4 But antibiotics, often broad spectrum,5 are prescribed for 60-80% of outpatient cases.3 This review examines the utility of antibiotics in improving symptoms and effecting clinical cure in adults with acute bronchitis.

Fifteen randomized controlled trials were included in this review. Antibiotics did not increase the number of subjects who were clinically improved or “cured” at follow up.* They did however decrease the percentage of patients with cough at a follow up visit (NNT=6). There was also a reduction in the duration of cough, days feeling ill, and days of limitations in daily activities, approximately one half of a day for each. Antibiotics slightly increased the number of patients with adverse effects (NNH=37)

Caveats: Acute bronchitis is defined as a cough-related illness lasting 1-3 weeks with or without sputum in an individual without chronic lung disease and a normal chest radiograph.1 It is one of the most common conditions for which patients consult a physician and the most common reasons for seeking care are symptom severity, duration, and interference with daily activities.2 Less than 10% of cases are thought to be bacterial, few patients cite needing an antibiotic, and most guidelines do not recommend their routine use in bronchitis.1 4 But antibiotics, often broad spectrum,5 are prescribed for 60-80% of outpatient cases.3 This review examines the utility of antibiotics in improving symptoms and effecting clinical cure in adults with acute bronchitis.

Fifteen randomized controlled trials were included in this review. Antibiotics did not increase the number of subjects who were clinically improved or “cured” at follow up.* They did however decrease the percentage of patients with cough at a follow up visit (NNT=6). There was also a reduction in the duration of cough, days feeling ill, and days of limitations in daily activities, approximately one half of a day for each. Antibiotics slightly increased the number of patients with adverse effects (NNH=37)


Figure 3 in the Cochrane review displays study data for this outcome measure. In its current form this forest plot suggests a small benefit in favor of antibiotics. However there are data entry errors for studies Stott 1976 and Verheij 1994, and the published meta-analysis for this outcome mistakenly employs a fixed effect rather than a random effects analysis, as the authors had intended (see p. 5 of the review for stated intentions regarding statistical analysis). These errors were confirmed with the Cochrane review lead author (personal communication January 5, 2012). When corrected this analysis and forest plot reveal no statistical benefit with antibiotics. Since these data are not available in the current Cochrane publication we have provided an amended figure 3 below:

Author: Koustav Mukherjee, MD

Published/Updated: January 30, 2012

  1. The Title Bar

    The title bar is color-coded with our overall recommendation.

    • Green: Benefits outweigh risks.
    • Yellow: Unclear risk/benefit profile.
    • Red: Benefits do not outweigh risks.
    • Black: Obvious harms, no clear benefits.
  2. Tip content...