Which of the following is NOT a non-depolarizing muscle relaxant?

Succinylcholine is classified as a depolarizing muscle relaxant, which distinguishes it from non-depolarizing muscle relaxants such as Atracurium, Mivacurium, and Tubocurarine. Depolarizing muscle relaxants work by binding to nicotinic acetylcholine receptors at the neuromuscular junction, causing a sustained depolarization of the muscle membrane. This initial depolarization leads to muscle fasciculations followed by paralysis.

In contrast, non-depolarizing muscle relaxants function by competitively blocking these receptors without activating them, preventing acetylcholine from binding and thus inhibiting muscle contraction. This fundamental difference in mechanism is what classifies Succinylcholine as a depolarizing agent and differentiates it from its non-depolarizing counterparts, all of which are utilized for their effects on muscle relaxation during surgical procedures or mechanical ventilation.