Is it better to add long-acting muscarinic antagonists or long-acting beta2-agonists to inhaled corticosteroids for people with uncontrolled asthma?

According to the Cochrane Airways Group an answer to this question is important as long-acting beta2-agonists (LABAs) can improve symptoms and reduce the likelihood of asthma attacks when inhaled corticosteroids are not helpful alone, but can have serious side effects.

Long-acting muscarinic antagonists (LAMAs) have confirmed efficacy in COPD and are now being considered as an alternative add-on therapy for people with uncontrolled asthma. 

In a review of the literature the group looked for randomised controlled studies that compared LAMA with LABA, both on top of inhaled corticosteroids, for at least 12 weeks.

From 8 studies that met inclusion criteria they found moderate quality evidence that LAMAs show small benefits over LABA on some measures of lung function, and high quality evidence that LABAs are slightly better for quality of life, but the differences were all small.

“Given the much larger evidence base for LABA versus placebo for people whose asthma is not well controlled on ICS, the current evidence is not strong enough to say that LAMA can be substituted for LABA as add-on therapy,” the group concluded.