Which of the following drugs is known to require caution in patients with bradycardia?

Verapamil is a calcium channel blocker primarily used to treat hypertension and certain types of cardiac arrhythmias. It acts by inhibiting the influx of calcium ions into cardiac muscle and vascular smooth muscle, leading to decreased contractility and vasodilation. Due to its effects on the heart's conduction system, verapamil can significantly lower heart rate and is known to cause bradycardia, especially in patients who already have a low heart rate.

In patients with bradycardia, the use of verapamil requires caution because it can exacerbate this condition, potentially leading to severe complications such as hypotension, syncope, or other arrhythmias. Therefore, monitoring and appropriate management of heart rate are essential when administering verapamil to individuals with bradycardia.

On the other hand, while other options listed may also affect heart function, they are generally less associated with inducing bradycardia in the same manner as verapamil. For example, clevidipine primarily acts as a vasodilator without significant effects on heart rate, while felodipine and nifedipine are mostly associated with peripheral vasodilation and are less likely to cause bradycardia.