Which antagonist (nondepolarizing) neuromuscular blocker is known to be vagolytic and should be prescribed cautiously?

Pancuronium is recognized as a vagolytic nondepolarizing neuromuscular blocker, which means it has the potential to block vagal tone, leading to increased heart rate through its affinity for muscarinic receptors. This property is significant, as it can result in elevated heart rates and may pose risks, particularly for patients with pre-existing cardiovascular conditions.

The vagolytic effect is derived from its action on the autonomic nervous system, where it can antagonize the actions of the vagus nerve, which is responsible for decreasing heart rate. Therefore, when prescribing pancuronium, it is essential to monitor the patient's cardiovascular status closely and use it judiciously.

In contrast, the other neuromuscular blockers listed—Vecuronium, Rocuronium, and Cisatracurium—do not possess significant vagolytic activity. They either have minimal cardiovascular effects or, in the case of Cisatracurium, are known for undergoing a metabolism that does not rely heavily on the liver or kidneys, thus making them safer alternatives in patients where vagal stimulation needs to be preserved.