Atrioventricular (AV) block can be caused by all of the following drugs EXCEPT:

Correct option is A

Ans. (a) Sol. Adenosine does not cause persistent AV block; rather, it is used to temporarily slow down AV nodal conduction in conditions like supraventricular tachycardia (SVT). The effects of adenosine are short-lived (lasting only a few seconds), and it does not result in a long-term AV block.
Explanation of Other Options:
· (b) Digitalis (Digoxin): Can cause AV block by increasing vagal tone and inhibiting the AV node, especially in toxic doses.
· (c) Calcium channel blockers (e.g., Verapamil, Diltiazem): Can lead to AV block by reducing calcium influx, which is essential for AV nodal conduction.
· (d) Beta-blockers (e.g., Metoprolol, Atenolol): Inhibit sympathetic stimulation of the AV node, slowing conduction and potentially causing AV block, especially in high doses or in patients with pre-existing conduction abnormalities.