Giving tiotropium to asthma patients who remained symptomatic despite treatment reduced the relative risk of acute exacerbation by 21%, according to a study published in the New England Journal of Medicine.
The phase III research, presented at the European Respiratory Society conference in Vienna, also showed adding the once-daily drug could cut the risk of any asthma exacerbation by 31%.
Tiotropium, a long-acting inhaled bronchodilator commonly used to treat COPD, is currently unlicensed for treating asthma.
In two trials supported by the drug's marketers, Boehringer Ingelheim and Pfizer, researchers recruited 912 patients with asthma already taking inhaled glucocorticoids and long-acting beta-agonists (LABAs).
Despite their drug regimen, all patients remained symptomatic and had at least one severe exacerbation within the past year.
Researchers randomised these patients to receive either tiotropium (5μg once daily) or placebo alongside their usual treatment. These were administed using a soft-mist inhaler.
The team found that after 24 weeks the average change in peak FEV1 from baseline was around 86ml greater among patients on tiotropium than placebo in the first trial, and 154ml greater in the second.
Patients receiving tiotropium went on average 282 days without a first exacerbation - 21% longer than those on placebo, who experienced an exacerbation within an average of 226 days. The effects were sustained over 24 hours.
Adverse events were similar between treatment and placebo groups.
The researchers concluded that 'in patients with poorly controlled asthma despite treatment with inhaled glucocorticoids and LABAs, adding tiotropium significantly reduced the risk of episodes of the worsening of asthma and asthma exacerbations requiring treatment with systemic glucocorticoids and provided sustained bronchodilation'.