Why are non-selective beta-blockers contraindicated in severe asthma?

Why are non-selective beta-blockers contraindicated in severe asthma?

• A. They block β2 receptors causing bronchoconstriction
• B. They cause tachycardia
• C. They increase airway mucus
• D. They are less effective antihypertensives

Answer: (A)

Non-selective beta-blockers block both beta-1 receptors in the heart and beta-2 receptors in the lungs. Blocking beta-2 receptors prevents the usual bronchodilation they produce, so the airways tend to constrict more. In severe asthma, this bronchoconstriction can trigger or worsen an attack and blunt the effectiveness of inhaled beta-agonist rescue meds, which rely on stimulating those same beta-2 receptors. That makes non-selective beta-blockers dangerous for someone with severe asthma. Other effects like tachycardia aren’t the primary concern here—these drugs actually slow the heart or reduce its workload in many cases, and they don’t increase airway mucus. They also aren’t avoided in asthma because of antihypertensive efficacy; the key issue is the potential for dangerous bronchospasm.

Non-selective beta-blockers block both beta-1 receptors in the heart and beta-2 receptors in the lungs. Blocking beta-2 receptors prevents the usual bronchodilation they produce, so the airways tend to constrict more. In severe asthma, this bronchoconstriction can trigger or worsen an attack and blunt the effectiveness of inhaled beta-agonist rescue meds, which rely on stimulating those same beta-2 receptors. That makes non-selective beta-blockers dangerous for someone with severe asthma.

Other effects like tachycardia aren’t the primary concern here—these drugs actually slow the heart or reduce its workload in many cases, and they don’t increase airway mucus. They also aren’t avoided in asthma because of antihypertensive efficacy; the key issue is the potential for dangerous bronchospasm.