Since oxidant damage may be critical in the pathophysiology of COPD, antioxidant therapy is a logical approach . Reactive oxygen species may be inhaled in cigarette smoke or generated by activated inflammatory cells within the lung, leading to reduced activity of antiproteases, increased production of inflammatory cytokines and direct inflammatory effects (Fig. 11.2). N-acetylcysteine was originally developed as a mucolytic, but has well documented antioxidant effects. Controlled trials have demonstrated that it reduces the frequency and severity of acute exacerbations of COPD , and in an open study it significantly reduced the rate of decline in lung function . It may therefore be useful in long-term management of COPD, but is not currently available on prescription in the UK. Further trials are indicated in patients with COPD who have more frequent exacerbations.
No studies with other antioxidants, such as vitamins C and E, have been reported in COPD. More effective antioxidants are now in development and should undergo clinical trials in COPD. It is likely that antioxidants may reduce the inflammation and proteolysis of COPD, resulting in reduced exacerbations, improved symptom control and a slowing of disease progression.
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