These recommendations are based on the National Institute for Health and Clinical Excellence (NICE) clinical guideline Management of chronic obstructive pulmonary disease in adults in primary and secondary care (partial update) [National Clinical Guideline Centre, 2010; NICE, 2010].

• NICE found evidence from a systematic review and three additional randomized controlled trials that mucolytics reduce exacerbation frequency and duration of disability in people with chronic bronchitis or chronic obstructive pulmonary disease (COPD). However, the quality of the evidence was low or very low, and benefits may occur only in people who are not receiving other maintenance treatments (for example inhaled corticosteroids). In view of this, the NICE guideline development group was concerned that a positive recommendation for the use of mucolytics purely to prevent exacerbations may preclude the use of other therapies which have a stronger evidence base, and incorrectly imply that mucolytics should be the first-line treatment for exacerbation prevention.
• The recommendation by NICE to only treat people with stable COPD who have a chronic cough productive of sputum seems to be based on evidence from a cost-effectiveness analysis that mucolytics are cost-effective in people with chronic bronchitis (regular cough with sputum production).