Suxamethonium chloride

Suxamethonium chloride, also known as succinylcholine chloride, is a medication used in medicine to induce muscle relaxation, primarily to facilitate tracheal intubation during general anesthesia or to provide muscle relaxation for short surgical procedures. It is a depolarizing neuromuscular blocker that acts by mimicking the action of acetylcholine at the neuromuscular junction, leading to muscle paralysis.

Mechanism of Action

Suxamethonium chloride acts on the nicotinic acetylcholine receptors at the neuromuscular junction. It mimics acetylcholine, a neurotransmitter, binding to these receptors and activating them. Unlike acetylcholine, suxamethonium is not rapidly degraded by acetylcholinesterase, which allows it to remain in the synaptic cleft, causing prolonged depolarization of the muscle endplate. This initial depolarization causes muscle fasciculations, followed by muscle paralysis.

Pharmacokinetics

After intravenous administration, the onset of action of suxamethonium is rapid, typically within 30 to 60 seconds, with a short duration of action of about 5 to 10 minutes. This short duration is due to the rapid hydrolysis of suxamethonium by plasma cholinesterase (also known as pseudocholinesterase or butyrylcholinesterase) into succinylmonocholine, which has a much lower neuromuscular blocking activity, and then further hydrolyzed to succinic acid and choline.

Clinical Uses

Suxamethonium is primarily used in anesthesia to facilitate endotracheal intubation during the induction of general anesthesia and to provide muscle relaxation during short surgical or diagnostic procedures. Its rapid onset and short duration of action make it particularly useful in emergency situations where rapid airway control is necessary.

Adverse Effects

While suxamethonium is generally safe when used by experienced practitioners, it can have several adverse effects. These include:

• Muscle pains or fasciculations
• Hyperkalemia, which can be dangerous in patients with pre-existing hyperkalemia or conditions predisposing to hyperkalemia
• Malignant hyperthermia, a rare but life-threatening condition triggered in susceptible individuals
• Bradycardia, especially with repeated doses
• Increased intraocular pressure, making it potentially hazardous in patients with glaucoma
• Prolonged paralysis in patients with atypical plasma cholinesterase

Contraindications

Suxamethonium is contraindicated in patients with a known hypersensitivity to the drug, personal or family history of malignant hyperthermia, acute narrow-angle glaucoma, penetrating eye injuries, and conditions predisposing to hyperkalemia.

History

Suxamethonium was first introduced in the 1950s and has since become one of the most commonly used muscle relaxants in anesthesia due to its rapid onset and short duration of action.

See Also

• Neuromuscular-blocking drug
• General anesthesia
• Acetylcholine
• Cholinesterase