A randomized, double-blind, placebo-controlled study evaluating the efficacy of propolis and N-acetylcysteine in exacerbations of chronic obstructive pulmonary disease.

Acute exacerbations of chronic obstructive pulmonary disease (AECOPDs) accelerate the progressive impairment of lung function and general health. Together with maintenance therapy for chronic obstructive pulmonary disease (COPD), N-acetylcysteine (NAC) and natural propolis have demonstrated pharmacological properties that address crucial pathophysiological processes underlying COPD and may prevent AECOPDs. This study aims at responding to dose-dependent efficacy and safety concerns regarding a propolis-NAC combination for the reduction of COPD exacerbation rates.This was a single-center, randomized, double-blind, phase IV trial with three treatment arms: Placebo and two active substance groups, one (AS-600) received 600 mg of NAC + 80 mg of propolis while the other (AS-1,200) received 1,200 mg of NAC + 160 mg of propolis. Following an AECOPD, frequent-exacerbation phenotype patients (n=46) were assigned a once-daily three-month therapy with the study drug and one year follow-up. The primary endpoint was the COPD exacerbation incidence rate during the follow-up period as a measure of dose-dependent efficacy of NAC-propolis combination compared to placebo.There was a statistically significant difference in the AECOPD incidence rate: 52.6% in patients that received placebo, 15.4% that received AS-600 and only 7.1% that received AS-1,200 (Fisher's exact test, p = 0.013). Compared to placebo, AECOPD frequency was significantly lower only in AS-1,200 (p=0.009). Compared to placebo, the relative risk for exacerbation was 0.29 in AS-600 and 0.13 in AS-1,200. No adverse events related to the treatment were reported.Oral combination of natural propolis with NAC confirmed formulation efficiency with a favorable safety profile. Our results need to be confirmed by larger clinical trials.