Macrolides for Treatment of Chronic Obstructive Pulmonary Disease
Chronic obstructive pulmonary disease (COPD) is a prevalent condition characterized by persistent airflow limitation, primarily caused by inflammation and autoimmune responses. Acute exacerbations of COPD (AECOPD) significantly increase the risk of mortality, accelerate the decline in lung function, and severely impair the quality of life. The inflammatory processes in COPD are not confined to the lungs but also affect multiple organ systems, leading to complications such as coronary heart disease, depression, and skeletal muscle atrophy. Clinical studies have demonstrated that long-term macrolide therapy can reduce the frequency of AECOPD. However, concerns regarding side effects such as drug resistance, cardiac toxicity, and hearing impairment have sparked debates about the safety and efficacy of prolonged macrolide use in COPD management.
Clinical Studies on the Effects of Macrolides on COPD
The concept of long-term macrolide therapy for COPD originated from its successful application in reducing exacerbations and improving lung function in patients with cystic fibrosis, diffuse panbronchiolitis, and other chronic respiratory diseases. Several randomized trials have shown that macrolide therapy effectively reduces the incidence of AECOPD. A systematic review highlighted the effectiveness and safety of prophylactic macrolides, particularly erythromycin, in decreasing the frequency of AECOPD. A retrospective study found that azithromycin significantly reduced AECOPD and hospitalizations in patients with severe COPD. Another study demonstrated that long-term use of low-dose erythromycin reduced interleukin-8 levels in the sputum of COPD patients and significantly decreased the number of acute exacerbations. Additionally, azithromycin was found to be more effective in older patients with milder disease stages, though it showed no significant benefit for inactive smokers. A 2014 systematic review concluded that long-term antibiotic therapy reduces AECOPD, but it remains unclear which specific subgroups of COPD patients benefit the most. Further subgroup analyses revealed that azithromycin (250 mg daily) was particularly effective in elderly COPD patients and those with milder stages of the disease, as classified by the Global Initiative for COPD (GOLD) guidelines. Gender and oxygen therapy did not significantly influence the efficacy of macrolides in these patients.
Anti-inflammatory Mechanism of Macrolides in COPD
The inflammatory mechanisms underlying COPD are complex and not fully understood. Macrolides have been shown to decrease mucus secretion and reduce the levels of neutrophils and macrophages in the airways by inhibiting the production of pro-inflammatory cytokines, adhesion molecules, and chemokines. Studies have also demonstrated that erythromycin can mitigate the inflammatory effects of COPD and counteract corticosteroid resistance induced by cigarette smoke extract. This is achieved through the inhibition of the phosphatidylinositol 3′-kinase-d/Akt pathway and the upregulation of histone deacetylase 2 expression. Recent research has highlighted the role of T lymphocyte imbalances in COPD patients and the ability of macrolides to partially correct abnormal immune responses in cigarette smoke-exposed mice. These findings suggest that macrolides exert their therapeutic effects by modulating inflammatory interleukins and immune responses, thereby reducing corticosteroid resistance in COPD treatment. However, the precise mechanisms of macrolides remain unclear, and further research is needed to fully elucidate their therapeutic potential.
Macrolides in Guidelines
Long-term macrolide therapy has been recommended in recent guidelines for the management of COPD. The European Respiratory Society and the American Thoracic Society have endorsed the use of long-term macrolides for COPD patients who experience more than one moderate-to-severe acute exacerbation annually, in addition to standard inhalation therapy. The 2017 GOLD guidelines suggest that macrolides, such as azithromycin (250 mg daily or 500 mg three times per week) or erythromycin (500 mg twice daily) for one year, can be considered for patients in Group D with a history of smoking and frequent exacerbations despite appropriate therapy. Studies have shown that low-dose erythromycin (125 mg daily) can inhibit airway inflammation and reduce AECOPD. Macrolides are particularly recommended for preventing AECOPD in patients with a history of recurrent acute exacerbations. However, the clinical application of macrolides in COPD still faces challenges that require further investigation.
Controversy of Long-Term Use of Macrolides in COPD Patients
While current evidence supports the use of continuous macrolide prophylaxis to significantly reduce COPD exacerbations and as a cost-saving strategy, concerns about adverse effects such as hearing impairment, arrhythmias, and antibiotic resistance persist. A retrospective cohort study reported a small absolute increase in cardiovascular deaths during a 5-day course of azithromycin therapy, with 47 additional cardiovascular deaths per 1 million courses compared to amoxicillin. For patients at the highest risk of cardiovascular disease, this number rose to 245 additional deaths per 1 million courses. Consequently, the U.S. Food and Drug Administration (FDA) has advised careful evaluation of patient-level risk factors for ventricular arrhythmias before prescribing azithromycin. Other side effects of macrolides include gastrointestinal symptoms, hearing decrement, and diarrhea. Hearing decrement is a leading cause of early withdrawal from macrolide therapy, although hearing function often returns to baseline in about one-third of patients. Given these risks, the use of lower doses of macrolides is recommended for COPD patients.
Incidence of Adverse Effects
The incidence of adverse effects associated with long-term azithromycin use in COPD remains uncertain. One study found no increased risk of cardiac arrhythmias over a one-year period with daily azithromycin compared to placebo. Published studies indicate that the majority of patients experiencing cardiac arrhythmias from macrolides had pre-existing risk factors, and the incidence of arrhythmias in the absence of such factors is very low, possibly less than one in 100,000 patients. This suggests that the risk of arrhythmias may have been overestimated, and with proper patient evaluation, chronic macrolide therapy can be safely used in most recommended cases.
Long-Term Use of Macrolides and Microbial Resistance
The widespread use of maintenance macrolide therapy in COPD raises concerns about the development of microbial resistance in community populations. Given the large number of COPD patients, the extensive use of macrolides, particularly azithromycin, could significantly impact population-level macrolide resistance. However, published studies have not yet provided evidence of the spread of drug-resistant bacteria, necessitating longer-term studies to monitor macrolide resistance in severe COPD patients and its effects on microbial populations and lower airway inflammatory responses.
Perspective
Macrolide therapy has been shown to reduce the rate of COPD exacerbations, prolong the time to the next exacerbation, and improve the quality of life for patients. However, the risk of serious adverse effects from long-term macrolide therapy in COPD remains uncertain. The anti-inflammatory effects of macrolides are believed to be the primary mechanism of action, though some researchers argue that macrolides also exert antibacterial effects and modulate airway microbiota. In China, the resistance rate to macrolides has reached 80%, differing from rates in European and American countries. Therefore, further clinical research is needed to better understand the mechanisms of macrolide therapy in COPD and its effects on lower airway inflammation.
The pathogenesis of COPD involves airway and lung inflammation. While anti-inflammatory drugs theoretically have the potential to control disease progression, glucocorticoids have not fully achieved this goal. Long-term macrolide therapy may offer additional benefits for COPD patients. Future research should focus on developing macrolides that can modify immune responses without exerting antibiotic effects, potentially offering a more targeted and safer therapeutic option for COPD management.
doi.org/10.1097/CM9.0000000000000248
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