neuromuscular blocker
A neuromuscular blocker is a drug that paralyzes skeletal muscle by interrupting the signal at the neuromuscular junction. Picture cutting the wire between nerve and muscle: the brain still gives the order, but the muscle cannot hear it, so it goes limp. These drugs are central to modern surgery.
They act on the muscle-type nicotinic acetylcholine receptor and come in two flavors. Non-depolarizing blockers, such as rocuronium and vecuronium, are competitive antagonists that simply occupy the receptor so acetylcholine cannot. Depolarizing blockers, chiefly succinylcholine, are agonists that overstimulate the receptor, causing a brief twitch and then a persistent depolarized state that the muscle cannot respond to.
Their purpose is to provide muscle relaxation for intubation, surgery, and mechanical ventilation; they have no effect on consciousness or pain, so they must always be combined with anaesthesia and analgesia. Because they can paralyze the breathing muscles, they are used only where the airway can be controlled.
Succinylcholine produces rapid, short-lived paralysis ideal for emergency intubation, letting clinicians secure the airway within about a minute.
A fast depolarizing blocker for emergency airways.
The two classes are reversed differently. Non-depolarizing block can be reversed by a cholinesterase inhibitor or, for rocuronium and vecuronium, by sugammadex, which wraps up the drug. Depolarizing block from succinylcholine cannot be reversed and must wear off on its own.