Rescue Inhaler Overuse in Severe Asthma: A Real-World Study of Short-Acting β2-Agonist and Short-Acting Muscarinic Antagonist Use

Background: Overuse of short-acting reliever inhalers, particularly short-acting β2-agonists (SABAs), is linked to poor asthma control, higher exacerbation risk, and increased mortality. Data on reliever overuse in severe asthma and the role of short-acting muscarinic antagonists (SAMAs) remain limited. Objective: This study aims to assess the prevalence of rescue inhaler overuse in adults with severe asthma and examine its associations with maintenance therapy adherence, biologic treatment, oral corticosteroid use, asthma control, lung function, allergic sensitization, and comorbidities. Methods: We conducted a retrospective observational study of 223 adults with severe asthma followed at a tertiary multidisciplinary clinic in 2024. Clinical, functional, pharmacological, and pharmacy-dispensing records were reviewed. Rescue inhaler overuse was defined as dispensing ≥ 3 SABA and/or SAMA canisters per 12 months. Associations with clinical and treatment variables were analyzed. Results: Among 223 patients, 144 (64.6%) had a prescribed rescue inhaler; 85 (38.1%) met the criteria for overuse. Of those prescribed rescue therapy, 59.0% overused, with 47.2% classified as low overuse and 11.1% as high overuse. Overuse was more frequent in patients with maintenance adherence > 50%. Biologic therapy was associated with reduced odds of overuse, while oral corticosteroid use showed no significant effect. Poor asthma control (ACT < 20) was strongly associated with overuse. Lung function did not differ significantly, though overusers tended to have lower FEV1. Allergic sensitization was not associated with overuse; bronchiectasis was the comorbidity most frequently linked. Conclusions: Rescue inhaler overuse is common in severe asthma and closely linked to inadequate disease control. Lower overuse rates among biologic-treated patients suggest improved control reduces reliance on short-acting relievers. Systematic monitoring of reliever use may help identify high-risk patients and guide individualized management strategies.