A Cochrane review included 17 studies with a total of 3 936 subjects with acute bronchitis, both smokers and non-smokers. Eight of the studies included only adults and the remaining studies included adolescents/children plus adults. Studies that included patients with pre-existing chronic bronchitis (i.e. acute exacerbation of chronic bronchitis) were excluded. For most studies, clinical findings were used to exclude patients thought to have pneumonia. Four studies used doxycycline, 4 erythromycin, 1 trimethoprim/sulfamethoxazole, 1 azithromycin, 1 cefuroxime, 1 amoxicillin or erythromycin, 2 amoxicillin, and 1 co-amoxiclav.
At follow-up, there was no difference in participants described as being clinically improved between antibiotic and placebo groups (table). Participants given antibiotics had a shorter mean cough duration, were less likely to have a cough, have a night cough, show no improvement on clinician's global assessment, or have abnormal lung findings. Antibiotic-treated patients also had a reduction in days feeling ill and a reduction in days with limited activity. No differences were observed in presence of a productive cough at follow up, proportions with activity limitations at follow up, and mean duration of productive cough. Adverse effects were increased in the antibiotic group. The most commonly reported side effects involved gastrointestinal symptoms such as nausea, vomiting or diarrhoea. Headaches, skin rash and vaginitis also occurred. Side effects seemed mild as only 0% to 13% (overall 3.7%) withdrew for this reason and no deaths were reported.
Authors' comment: The magnitude of the modest beneficial effect of antibiotics in patients with acute bronchitis needs to be considered in the broader context of potential side effects, medicalization for a self-limiting condition, increased resistance to respiratory pathogens and cost of antibiotic treatment. It is possible that older patients with multimorbidities may not have been recruited to trials so the evidence guiding decision making in this group of patients is less certain.
| Outcome | Participants (studies) | Antibiotics* | Placebo* | RR (95% CI) | NNT |
|---|---|---|---|---|---|
| *crude prevalence | |||||
| Clinically improved | 3 841 (11) | 73% | 67% | 1.07 (0.99 to 1.15) | 22 |
| Cough at follow-up visit | 275 (4) | 33% | 51% | 0.64 (0.49 to 0.85) | 6 |
| Night cough at follow-up visit | 538 (4) | 30% | 45% | 0.67 (0.54 to 0.83) | 7 |
| Productive cough at follow-up visit | 713 (7) | 37% | 37% | 0.97 (0.82 to 1.16) | |
| Limitation in work or activities at follow-up visit | 478 (5) | 10% | 14% | 0.75 (0.46 to 1.22) | |
| Not improved by physician's global assessment at follow-up visit | 891 (6) | 14% | 23% | 0.61 (0.48 to 0.79) | 25 |
| Abnormal lung exam at follow-up visit | 613 (5) | 18% | 35% | 0.54 (0.41 to 0.70) | 6 |
| Adverse effects | 3 496 (12) | 23% | 19% | 1.20 (1.05 to 1.36) | 5 |
| Outcome | Participants (studies) | Mean difference (95% CI) | |||
| Mean number of days of cough | 2 776 (7) | –0.46 (–0.87 to –0.04) days | |||
| Mean number of days of productive cough | 699 (6) | –0.43 (–0.93 to 0.07) days | |||
| Mean number of days of impaired activities | 767 (6) | –0.49 (–0.94 to –0.04) days | |||
| Mean number of days of feeling ill | 809 (5) | –0.64 (–1.16 to –0.13) days | |||
Comment: The quality of evidence is downgraded by inconsistency (variability in results).
Clinical comment: Testing acute phase reactants (CRP) might assist in identifying patients who do not benefit from antibiotics from those for whom antibiotics could be considered.