Background and objective: Non-selective beta-blockers impair the bronchodilator response to beta2 -agonists. Cardio-selective beta1 -blockers are less likely to cause this effect, yet they remain relatively contraindicated in asthma. We investigated whether the response to salbutamol is impaired during cardio-selective beta1 -blocker treatment in people with asthma.
Methods: A random-order, double-blind, placebo-controlled, non-inferiority, crossover study was conducted comparing up to 5 mg bisoprolol daily for 2 weeks with matching placebo, with an open-label extension of up to 10 mg bisoprolol daily. After each treatment period, mannitol was inhaled to induce bronchoconstriction with a 15% fall in forced expiratory volume in 1 s (FEV1 ). Immediately after mannitol challenge, salbutamol (100, 100 and 200 μg) was administered via spacer at 5-min intervals with repeated FEV1 measures. The FEV1 recovery with salbutamol was measured as an area under recovery curve (AUC). Based on earlier research, a clinically relevant non-inferiority limit of a 30% reduction in the AUC was set.
Results: A total of 19 adults with mild asthma and positive inhaled mannitol challenge completed the study. Adjusting for the FEV1 fall induced by mannitol and treatment sequence, the mean AUC response to salbutamol after bisoprolol was 5% lower than after placebo, with a one-sided 95% confidence interval (CI) of 26% lower. Thirteen participants completed the open-label extension up to 10 mg bisoprolol daily with mean AUC 11% higher after bisoprolol with a 95% CI of 5% lower.
Conclusion: The bronchodilator response to rescue salbutamol after mannitol-induced bronchoconstriction is non-inferior during regular treatment with the cardio-selective beta1 -blocker, bisoprolol, compared to placebo.
Clinical trial registration: ACTRN12618000306213 at https://www.anzctr.org.au.
Keywords: adrenergic beta-antagonists beta-blocker; adrenergic beta2-receptor agonists; asthma; bisoprolol; salbutamol.
© 2020 Asian Pacific Society of Respirology.