Plain language summary
Chronic obstructive pulmonary disease (COPD) is characterised by reduced airflow, excess mucus secretion and shortness of breath. During exacerbations, excessive free radicals are formed leading to reduced levels of the body’s glutathione (GSH) antioxidant system. N-acetylcysteine (NAC) is a precursor to GSH and also a well-known mucolytic agent. The aim of this meta-analysis, which included 9 randomised, placebo-controlled trials with 2137 COPD patients, was to evaluate the effectiveness of NAC supplementation. Outcome measures were number of patients with no acute exacerbations, change in forced expiratory volume at 1s (FEV1), change in forced vital capacity (FVC), St George’s Respiratory Questionnaire, change in glutathione levels and adverse events. There was no statistically significant difference between the NAC and the placebo group in any of the outcomes. This was regardless of dose, which ranged from 600 mg every 24 hours to 1800 every 12 hours. Limitations of this meta-analysis, as listed by the authors, include the small number and sizes of studies and the heterogeneity of study designs.
Abstract
BACKGROUND N-acetylcysteine (NAC) may reduce acute exacerbations of chronic obstructive pulmonary disease through an antioxidant effect. Due to the heterogeneity in studies, the currently available data do not confirm the efficacy of oral NAC therapy in chronic obstructive pulmonary disease patients. We hypothesize that chronic obstructive pulmonary disease patients receiving regular oral NAC therapy do not achieve improved clinical outcomes. OBJECTIVES The purpose of this meta-analysis was to determine the efficacy of long-term oral NAC therapy in chronic obstructive pulmonary disease patients. DATA SOURCES AND METHODS The literature search was performed using the PubMed, Web of Science, and Cochrane Library databases to identify all included clinical studies. Studies were eligible for inclusion only if they directly compared the outcomes of NAC versus placebo in adults with chronic obstructive pulmonary disease between 1 January 2000 and 30 May 2022. All studies were included if they reported one or more of the following outcomes: number of patients with no acute exacerbations, forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), St George's Respiratory Questionnaire score, glutathione level, and adverse events. RESULTS Nine randomized controlled trials were included in the meta-analysis. There were 1061 patients in the NAC group and 1076 patients in the placebo group. The current meta-analysis provides evidence that the number of patients with no acute exacerbations (965 patients receiving NAC therapy, 979 control group patients), change in FEV1 (433 patients receiving NAC therapy, 447 control group patients), change in FVC (177 patients receiving NAC therapy, 180 control group patients), change in St George's Respiratory Questionnaire score (128 patients receiving NAC therapy, 131 control group patients), change in glutathione levels (38 patients receiving NAC therapy, 40 control group patients), and adverse events (832 patients receiving NAC therapy, 846 control group patients) were not significantly different between the two groups. CONCLUSION NAC did not reduce the risk of acute exacerbation or ameliorate the decline in lung volume in chronic obstructive pulmonary disease patients.
Methodological quality
Jadad score
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Not applicable
Allocation concealment
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Not applicable
