succinylcholine

Succinylcholine, also known as suxamethonium chloride, is a depolarizing neuromuscular blocking agent used to produce brief, pronounced muscle paralysis for rapid airway control during anesthesia, most commonly for rapid sequence induction and endotracheal intubation.

Mechanism of action is through direct agonist activity at nicotinic acetylcholine receptors at the motor endplate. It causes an initial muscle fasciculation followed by sustained depolarization of the junction, rendering the muscle unable to respond to further stimulation and resulting in flaccid paralysis. The effect is ultra-short acting because succinylcholine is rapidly hydrolyzed by plasma cholinesterase (butyrylcholinesterase) in the blood. With prolonged exposure or repeated dosing, a desensitizing phase (phase II block) can occur, which has different clinical implications.

Pharmacokinetics: onset is typically within 30 to 60 seconds, with a duration of about 5 to 10 minutes in healthy individuals. Metabolism occurs mainly via plasma cholinesterases; genetic variants or deficiencies, liver disease, or certain drugs can prolong the effect.

Clinical use and cautions: it is valued for situations requiring rapid and brief paralysis, but it provides no analgesia or sedation, so anesthesia is required. It is contraindicated in individuals with susceptibility to malignant hyperthermia and in conditions associated with an elevated risk of hyperkalemia, such as significant burns, denervation injuries, extensive trauma, or certain neuromuscular diseases. It also increases intraocular and intragastric pressure and may cause muscle fasciculations and postoperative myalgia.

Adverse effects and interactions: common issues include fasciculations, postoperative myalgia, bradycardia or other rhythm disturbances, hyperkalemia, and rare malignant hyperthermia. Drugs that inhibit butyrylcholinesterase or otherwise affect cholinesterase activity can prolong its effect, and some antibiotics may enhance neuromuscular blockade.

Names and history: marketed as Anectine in the United States and as suxamethonium chloride in other regions; introduced in the mid-20th century and remains in use in certain settings, though alternatives are increasingly common.