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Oral mucolytic drugs for exacerbations of chronic obstructive pulmonary disease: systematic review

BMJ 2001; 322 doi: (Published 26 May 2001) Cite this as: BMJ 2001;322:1271
  1. Phillippa J Poole, senior lecturer (p.poole{at},
  2. Peter N Black, associate professor
  1. Department of Medicine, University of Auckland, Private Bag 92019, Auckland, New Zealand
  1. Correspondence to: P J Poole
  • Accepted 28 February 2001


Objective: To assess the effects of oral mucolytics in adults with stable chronic bronchitis and chronic obstructive pulmonary disease.

Design: Systematic review of randomised controlled trials that compared at least two months of regular oral mucolytic drugs with placebo.

Studies: Twenty three randomised controlled trials in outpatients in Europe and United States.

Main outcome measures: Exacerbations, days of illness, lung function, adverse events.

Results: Compared with placebo, the number of exacerbations was significantly reduced in subjects taking oral mucolytics (weighted mean difference −0.07 per month, 95% confidence interval −0.08 to −0.05, P<0.0001). Based on the annualised rate of exacerbations in the control subjects of 2.7 a year, this is a 29% reduction. The number needed to treat for one subject to have no exacerbation in the study period would be 6. Days of illness also fell (weighted mean difference −0.56, −0.77 to −0.35, P<0.0001). The number of subjects who had no exacerbations in the study period was greater in the mucolytic group (odds ratio 2.22, 95% confidence interval 1.93 to 2.54, P<0.0001). There was no difference in lung function or in adverse events reported between treatments.

Conclusions: In chronic bronchitis and chronic obstructive pulmonary disease, treatment with mucolytics is associated with a reduction in acute exacerbations and days of illness. As these drugs have to be taken long term, they could be most useful in patients who have repeated, prolonged, or severe exacerbations of chronic obstructive pulmonary disease.

What is already known on this topic

What is already known on this topic Mucolytic drugs have properties that may be beneficial in chronic obstructive pulmonary disease

These drugs are not prescribed in the United Kingdom and Australasia, although they are widely used in many other countries

Drugs that reduce exacerbations may reduce the morbidity and healthcare costs associated with progressively severe disease

What this study adds

What this study adds Regular use of mucolytic drugs for at least two months significantly reduces exacerbations and days of illness compared with placebo in patients with chronic bronchitis and chronic obstructive pulmonary disease

Exacerbations that do occur may not be as severe, and the benefit may be greater in those with more severe disease

Reductions are modest and treatment may not be cost effective


  • Funding None

  • Competing interests None declared.

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