Mucolytic agents for chronic bronchitis or chronic obstructive pulmonary disease

  • Review
  • Intervention




Individuals with chronic bronchitis or chronic obstructive pulmonary disease (COPD) may suffer recurrent exacerbations with an increase in volume and/or purulence of sputum. Because of the personal and healthcare costs associated with exacerbations, any therapy that reduces the number of exacerbations is useful. There is a marked difference between countries in terms of prescribing of mucolytics depending on whether or not they are perceived to be effective.


To assess the effects of oral mucolytics in adults with stable chronic bronchitis or COPD.

Search strategy

We have searched the Cochrane Airways Group Specialised Register and reference lists of articles on four separate occasions, the most recent being in June 2007.

Selection criteria

Randomised trials that compared oral mucolytic therapy with placebo for at least two months in adults with chronic bronchitis or COPD. Studies of people with asthma and cystic fibrosis were excluded.

Data collection and analysis

One review author extracted data. Study authors and drug companies were contacted for missing information.

Main results

Twenty six trials involving 7335 participants were included. Compared with placebo, there was a significant reduction in the number of exacerbations per patient with oral mucolytics (weighted mean difference (WMD) -0.05 per month, 95% confidence interval -0.05 to -0.04). Using the annualised rate of exacerbations in the control patients of 2.6 per year, this is a 20% reduction. The number of days of disability also fell (WMD -0.56, 95% confidence interval -0.77 to -0.35). A recent study has shown that the benefit may apply only to those patients not already receiving inhaled corticosteroids. The number of patients who remained exacerbation-free was greater in the mucolytic group (OR 2.13 (95% CI 1.86 to 2.42)). There was no difference in lung function or in adverse effects reported between the treatments.

Authors' conclusions

In participants with chronic bronchitis or COPD, treatment with mucolytics was associated with a small reduction in acute exacerbations and a reduction in total number of days of disability. Benefit may be greater in individuals who have frequent or prolonged exacerbations, or those who are repeatedly admitted to hospital with exacerbations with COPD. They should be considered for use, through the winter months at least, in patients with moderate or severe COPD in whom inhaled corticosteroids (ICS) are not prescribed.

Plain language summary

Mucolytic agents for chronic bronchitis or chronic obstructive pulmonary disease

Twenty six trials with 7335 participants were included. The evidence suggests that if patients take the medicines regularly through the winter months this could result in a 20% reduction in these episodes (approximately 0.6 fewer per year), especially in people not already taking inhaled corticosteroids. There is considerable variation between the results of different studies in this review that is not fully explained. These medicines do not affect the loss of lung function in COPD, but they are very safe and well tolerated.