N-acetylcysteine Treatment in Chronic Obstructive Pulmonary Disease (COPD) and Chronic Bronchitis/Pre-COPD: Distinct Meta-analyses

Introduction: N-acetylcysteine (NAC) is a mucolytic agent with antioxidant properties. Oxidative stress is a key pathogenic mechanism in chronic respiratory conditions such as COPD and chronic bronchitis (CB). In these meta-analyses we investigated the efficacy of NAC in subjects with COPD or CB, the latter being a potential pre-COPD condition (CB/pre-COPD). Methods: The meta-analyses were conducted according to PRISMA guidelines. Exacerbations were assessed using total number of exacerbations. Improvement in patients' respiratory symptoms and/or patients quality of life (QoL) were measured by validated tools or assessed at the end of the study. Results: Twenty studies were included, of which seven evaluated NAC in patients with symptoms of CB/pre-COPD as entry criterion. NAC treated patients showed a significant reduction of the incidence of exacerbations as compared to placebo both in COPD (IRR=0.76; 95% confidence interval (CI) 0.59-0.99) and CB/pre-COPD (IRR=0.81; 95% CI 0.69-0.95). Sensitivity analyses in studies with duration higher than 5 months, confirmed the overall results. CB/pre-COPD patients treated with NAC were significantly more likely to experience an improvement in symptoms and/or QoL compared to placebo (odds ratio (OR)=3.47; 95% CI 1.92-6.26). A similar trend was observed in the few COPD studies evaluable. Sensitivity analyses showed a significant association of NAC with improvement in symptoms and/or QoL both in CB/pre-COPD and COPD patients. Conclusions: These findings provide novel data of NAC on the improvement in symptoms and QoL in addition to prevention of exacerbations in COPD and CB/pre-COPD. PROSPERO registry no. CRD42023468154.