Suxamethonium
A depolarizing neuromuscular blocker that acts within a minute and lasts minutes, used for rapid tracheal intubation; succinylcholine in the US.
Also called succinylcholine (US name).
Drug card
- How it works
- Depolarizing the motor end-plate and keeping it depolarized, so muscle goes limp
- Used for
- Rapid tracheal intubation, as in emergencies
- Short muscle relaxation for surgery or ventilation
- Known for
- High potassium, dangerous after burns, trauma or denervation
- Malignant hyperthermia
- Prolonged apnea with low or atypical plasma cholinesterase
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does suxamethonium work?
Suxamethonium binds end-plate nicotinic receptors like acetylcholine and depolarizes the membrane, causing visible fasciculations, then flaccid paralysis while the drug remains (phase I block). Paralysis starts in under a minute and lasts about 4 to 6 minutes, as plasma cholinesterase hydrolyzes it fast. Repeated or prolonged dosing can bring phase II block and tachyphylaxis.
Uses
What is suxamethonium used for?
- Rapid tracheal intubation, as in emergencies
- Short muscle relaxation for surgery or ventilation
Side effects
Side effects of suxamethonium
- High potassium, dangerous after burns, trauma or denervationKnown forSerious
- Malignant hyperthermiaKnown forSerious
- Prolonged apnea with low or atypical plasma cholinesteraseKnown forSerious
- Muscle pains after surgery
- Muscle twitching (fasciculations)
- Slow heart rate, especially after a second doseSerious
- Raised pressure in the eye
- Rhabdomyolysis in children with hidden myopathySerious
- Ventricular arrhythmias and cardiac arrestSerious
- AnaphylaxisSerious
- Excess salivation
- Rash
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in skeletal muscle myopathies and when malignant hyperthermia susceptibility is known or suspected, in the patient or family.
- Avoid after the acute phase of major burns, multiple trauma, denervation or upper motor neuron injury.
- Low or atypical plasma cholinesterase prolongs apnea; neostigmine does not reverse phase I block and can deepen it.
- In children, keep it for emergency airway control: hidden myopathy can cause hyperkalemic cardiac arrest.
Good to know: Its onset within a minute and brief action suit emergency intubation. With halogenated inhaled anesthetics, it is one of the principal drug triggers of malignant hyperthermia.
Remember it
A way to remember it
HAMMER
- H
- Hyperkalemia
- A
- Apnea that lasts when plasma cholinesterase is low
- M
- Malignant hyperthermia
- M
- Muscle pains after surgery
- E
- Eye pressure rises
- R
- Rhabdomyolysis in hidden muscle disease
Written for biofideX
Its class
Depolarizing neuromuscular blockers
A depolarizing blocker binds the nicotinic receptors of the motor end-plate as acetylcholine does and depolarizes it, so muscles first twitch (fasciculations), then go flaccid while the drug remains (phase I block). Plasma cholinesterase breaks suxamethonium down within minutes. Repeated or prolonged dosing can turn this into a phase II block that resembles a non-depolarizing one.
Easily mixed up with non-depolarizing neuromuscular blockers, anticholinesterases and inhaled anesthetics.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Succinylcholine chloride injection: label (DailyMed)
- Suxamethonium chloride 50mg/ml solution for injection: SmPC (emc)
- Atracurium besylate injection: label (DailyMed)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Anesthesia and muscle relaxants
Suxamethonium is one of 8 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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