Mucolytic agents for chronic bronchitis or chronic obstructive pulmonary disease

  • Review
  • Intervention


  • PJ Poole,

  • PN Black

Dr Phillippa Poole, Associate Professor in Medicine, University of Auckland, Private Bag 92019, Auckland, NEW ZEALAND.



Individuals with chronic bronchitis or chronic obstructive pulmonary disease (COPD) may suffer recurrent exacerbations with an increase in volume and/or purulence of sputum and any therapy that reduced the number of exacerbations would be 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 trials register and reference lists of articles, on three separate occasions.

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 reviewer extracted data. Study authors and drug companies were contacted for missing information.

Main results

Twenty three trials were included. Compared with placebo, there was a significant reduction in the number of exacerbations per patient with oral mucolytics (weighted mean difference (WMD) -0.066 per month, 95% confidence interval -0.077, -0.054, p<0.001). Using the annualised rate of exacerbations in the control patients of 2.7 per year, this is a 29% reduction. The number of days of disability also fell (WMD -0.56, 95% confidence interval -0.77, -0.35, p<0.001). The number of patients who remained exacerbation-free was greater in the mucolytic group (OR 2.22, 95% confidence interval 1.93, 2.54, p<0.001). There was no difference in lung function or in adverse effects reported between treatments.

Authors' conclusions

In subjects with chronic bronchitis or COPD, treatment with mucolytics was associated with a small reduction in acute exacerbations and a somewhat greater reduction in total number of days of disability.

Plain language summary

Plain language summary

This review looks at whether medicines that are believed to make phlegm (sputum) easier to cough up reduce the number of times patients with chronic bronchitis have a flare up of their disease. It shows that if patients take the medicines regularly this could result in a 29% reduction in these episodes. This is approximately 0.8 less episodes per patient per year.