Abstractprescription of mucoactive drugs for chronic obstructive pulmonary disease (copd) is increasing. this development in clinical practice arises, at least in part, from a growing understanding of the important role that exacerbation frequency, systemic inflammation and oxidative stress play in the pathogenesis of respiratory disease. s-carboxymethylcysteine (carbocisteine) is the most frequently prescribed mucoactive agent for long-term copd use in the uk. in addition to its mucoregulatory activity, carbocisteine exhibits free-radical scavenging and anti-inflammatory properties. these characteristics have stimulated interest in the potential that this and other mucoactive drugs may offer for modification of the disease processes present in copd.