Because there is a solid pharmacological rationale based on positive interactions between long-acting muscarinic receptor antagonists (LAMAs) and long-acting β-agonists (LABAs) for their ability to relax human airway smooth muscle in vitro alongside several randomised controlled trials (RCTs) and real-world observational studies that support the use of LAMA/LABA fixed-dose combinations (FDCs) for the treatment of patients with chronic obstructive pulmonary disease (COPD), in this narrative review we discuss the preclinical and clinical proofs supporting the use of LAMA + LABA therapy in COPD and why this therapeutic approach optimises bronchodilation. Robust evidence indicates that all LAMA/LABA FDCs are consistently more effective than LAMA or LABA administered alone in improving lung function, dyspnoea, quality of life and exercise capacity in patients with COPD. However, the ability of dual bronchodilation with FDCs of LAMA/LABA to prevent or reduce the risk of COPD exacerbations remains unclear due to conflicting data from large RCTs, despite several mechanisms explaining why such combinations should be of value in decreasing the frequency of COPD exacerbations. Both LABAs and LAMAs mechanistically can affect the cardiovascular system, but from clinical studies to date, LAMA/LABA FDCs have an acceptable cardiovascular safety profile, at least in the COPD population enrolled in RCTs. Indirect evidence suggests that some FDCs may even exert a protective role against serious cardiovascular adverse events compared to monotherapies. Consequently, several LAMA/LABA FDCs have been developed and approved for clinical use as treatments for patients with COPD. However, to date, there are unfortunately very few head-to-head studies comparing the safety and efficacy of different LAMA/LABA FDCs, making it difficult to choose the most appropriate combination, although the use of meta-analyses has provided some information in this regard. Endurance time Exercise time until exhaustion measured by a standard endurance test. Inspiratory capacity The maximum volume of air that can be inspired after reaching the end of a normal, quiet expiration. It is the sum of the tidal volume and the inspiratory reserve volume. St George's Respiratory Questionnaire (SGRQ) A tool to measure health status in patients with respiratory disease. It has three domains: symptoms, activity and impacts. A total score is also calculated. A minimal important difference (range) of ∼4 (2.4-5.6) units in the SGRQ total score is supported by published studies. Surface under the cumulative ranking curve analysis (SUCRA) A numerical representation of the overall rating that displays a single value for each treatment. SUCRA levels vary from 0% to 100%. The higher the SUCRA value and the closer it is to 100%, the more likely therapy is in the top rank or one of the top rankings; the lower the SUCRA value and the closer it is to 0%, the more likely therapy is in the bottom rank or one of the bottom ranks. Transition dyspnoea index (TDI) Widely used in clinical studies of COPD to measure shortness of breath, indicating change in response to an intervention. The total score ranges from −9 to 9; the negative value indicates deterioration, whereas a positive value indicates improvement. There is sufficient evidence to suggest that the minimal important difference for the TDI score is 1 unit. Trough FEV1 The mean volume of air that can be forced out in 1 second approximately 12 (with a twice-daily agent) or 24 (with a once-daily agent) hours after the last administration of bronchodilator.
- fixed-dose combinations