Mucolytic Drugs for Chronic Bronchitis and(COPD)

Mucolytic Drugs for Chronic Bronchitis and Chronic Obstructive Pulmonary Disease (COPD)

Importance of the Topic:
Chronic obstructive pulmonary disease (COPD) and chronic bronchitis are ongoing respiratory conditions. They cause symptoms such as breathlessness, coughing, and increased mucus production. People with COPD and chronic bronchitis may experience exacerbations when their symptoms worsen.

Mucolytics are oral medications that reduce the thickness of mucus, making it easier to clear. Mucolytics may have additional positive effects on infection and lung inflammation, potentially reducing exacerbations in individuals with COPD and chronic bronchitis. Inhalation of mucolytics is also possible, but inhalation mucolytics are not discussed in this review.

Study Characteristics:

We searched for studies lasting at least two months that randomly assigned individuals to receive a mucolytic drug or a placebo. Studies including children or individuals with other respiratory conditions such as asthma and cystic fibrosis were not included.

We found 38 studies to include in our review. These studies included a total of 10,377 adults with COPD or chronic bronchitis. The studies included various mucolytic drugs, including N-acetylcysteine, carbocysteine, and erdosteine, with durations ranging from two months to three years. Mucolytics were taken orally once to three times daily. These studies measured several different outcomes to determine if the drug was beneficial, including exacerbations, recovery, quality of life, lung function, and side effects.

Key Findings:

We found that individuals taking mucolytic therapy experienced fewer exacerbations compared to those taking the placebo. Approximately eight individuals needed to take the drug for nine months to prevent one additional exacerbation. This result was based on 28 studies involving 6723 participants. However, earlier studies (from the 1970s to the 1990s) showed greater benefits than recent studies. Shorter studies also showed greater benefits compared to longer studies. This may be because newer studies were more comprehensive and showed that mucolytics were less beneficial than previously thought. Alternatively, before 2000, when there was an incentive to report all trial results, whether they showed benefit or not, only studies showing mucolytics were beneficial were published.

There were fewer days of disability (days when individuals were unable to carry out their daily activities) for individuals taking mucolytics each month, but this was a very small difference—less than half a day per person per month. The likelihood of hospitalization also decreased by approximately a third, although this result was based only on five studies providing this information.

The study results indicate that mucolytics do not significantly affect quality of life or lung function. Individuals taking mucolytics did not experience more unwanted side effects compared to those taking the placebo. However, we were unable to confirm their effect on mortality rates during the study period, as only 35 deaths occurred among 3527 participants in studies where deaths were recorded.

Quality of Evidence:
We have moderate confidence in the results we presented. Our confidence is diminished due to the variability of individual study results, as well as the mixture of older and newer studies we found. Additionally, in some cases, there was insufficient data to be confident whether mucolytic treatments were better, worse, or equally effective as the placebo.


Mucolytics appear to be beneficial in reducing exacerbations, disability days, and recovery in individuals with COPD or chronic bronchitis, and they do not seem to cause additional unwanted side effects. However, they do not appear to have a significant impact on quality of life or lung function, and we were unable to confirm their effect on mortality rates.