Which drug is contraindicated for asthmatics with stable SVT?

• A. Adenosine
• B. Amiodarone
• C. Atropine
• D. Lidocaine

Answer: (A)

Adenosine should be avoided in asthma because it can trigger bronchospasm, making it contraindicated for asthmatic patients with stable SVT. Adenosine rapidly slows AV node conduction to interrupt AV-nodal reentrant SVT, but in the airways it can cause bronchoconstriction by activating receptors on airway smooth muscle, releasing mediators that worsen asthma symptoms. In a patient with asthma, this bronchospasm risk outweighs the benefit, so an alternative such as amiodarone is typically considered if the rhythm needs management. The other drugs don’t fit for this situation: atropine targets bradycardia and won’t reliably terminate SVT, while lidocaine is used for ventricular arrhythmias, not narrow-complex SVT.