P7. Mucolytic agents

Mucolytics may reduce the frequency and duration of exacerbations (Poole and Black, 2010) [evidence level II]

Mucolytics, including N-acetylcysteine (NAC), ambroxol (3), sobrerol, carbocysteine, sobrerol, letosteine, cithiolone, iodinated glycerol, N-isobutyrylcysteine (NIC), myrtol and erdosteine have multiple possible actions in COPD including decreasing sputum viscosity, and antioxidant, anti-inflammatory or antibacterial activity. A recently updated Cochrane review (Poole and Black, 2010) included 9 studies in COPD and 19 studies in chronic bronchitis. The authors found treatment with mucolytics was associated with a small reduction in acute exacerbations, WMD -0.05 per month (95% CI -0.05 to -0.03) and a reduction in total number of days of disability WMD -0.56 (95% CI -0.77 to -0.35). This equated to a NNT of 6 to prevent one exacerbation over winter months, and they concluded mucolytics should be considered for use through the winter months at least, in patients with moderate or severe COPD in whom inhaled glucocorticoids are not prescribed. The caveat on the use of inhaled glucocorticoids was their belief that this was the cause of the decline in the observed effect of mucolytics over time. This is in keeping with a recent trial of 709 subjects with COPD randomised to carbocisteine or placebo (Zheng 2008), which found a significant decrease in exacerbations (risk ratio 0.75, 95% CI 0.62 to 0.92, p=0.004) in subjects where the use of inhaled glucocorticoids was only 15% in the placebo and 18% in the carbocisteine arms (Zheng et al., 2008) [evidence level II].