Which drug is a non-depolarizing neuromuscular blocker?

• A. Vecuronium
• B. Succinylcholine
• C. Propofol
• D. Ketamine

Answer: (A)

Non-depolarizing neuromuscular blockers work by competitively blocking acetylcholine receptors at the neuromuscular junction. They prevent acetylcholine from binding, so the motor endplate cannot depolarize, leading to muscle paralysis without the initial fasciculations seen with depolarizing agents. Vecuronium is a classic example of this type: it occupies the nicotinic receptors and stops depolarization, producing relaxation that can be reversed with acetylcholinesterase inhibitors (often with an anticholinergic to block muscarinic effects).

In contrast, succinylcholine is depolarizing: it acts as an agonist at the same receptor, causing an initial depolarization and fasciculations, then a desensitized, prolonged block. It has a rapid onset but a short duration and isn’t reversed by standard acetylcholinesterase inhibitors, and it carries different risks such as malignant hyperthermia in susceptible individuals.

Propofol and ketamine are anesthetic agents, not dedicated neuromuscular blockers, so they don’t produce the targeted receptor blockade used to paralyze muscles in a controlled way.