When to use suxamethonium

5 min read Last updated April 8, 2026

What suxamethonium is (and why we use it)

  • Suxamethonium (succinylcholine) is a depolarising neuromuscular blocker: it causes a brief muscle twitching (fasciculations) then paralysis.
  • Very fast onset (often ~30–60 seconds) and short duration (often ~5–10 minutes) because it is broken down by plasma cholinesterase.
  • Main advantage: rapid, reliable intubating conditions with quick offset if intubation fails (but you must still be ready to ventilate and follow failed intubation plans).

Common situations where suxamethonium is a good choice

  • Rapid sequence induction (RSI) when you want the fastest possible intubation conditions (e.g., high aspiration risk).
  • When you anticipate a short procedure requiring intubation and rapid return of breathing is useful (case-by-case; many short cases can use rocuronium + sugammadex instead).
  • When you need immediate muscle relaxation and you do not have sugammadex available or it is contraindicated (local policy dependent).
  • Emergency airway situations where speed matters and you have assessed that contraindications are unlikely.

When to consider alternatives instead (often rocuronium)

  • If there is any significant risk of dangerous hyperkalaemia (see red flags) — choose a non-depolarising agent (commonly rocuronium).
  • If there is a personal or strong family history of malignant hyperthermia — avoid suxamethonium.
  • If there is a high risk of severe bradycardia (especially in children, or with repeat dosing) — consider alternatives and ensure atropine is available if using.
  • If difficult airway is anticipated and you are planning an awake technique or maintaining spontaneous ventilation — suxamethonium is usually not part of that plan.

Pre-dose checks (new-starter safe routine)

  • Confirm indication: what is the airway plan and why do you need rapid paralysis?
  • Screen for contraindications: burns, paralysis/neuromuscular disease, prolonged immobility/ICU stay, major crush injury, severe infection with muscle breakdown, previous suxamethonium reaction, malignant hyperthermia risk.
  • Check potassium (K+) if there is any reason it could be high (renal failure, tissue injury, prolonged immobility, neuromuscular disease). If unsure, pause and ask a senior.
  • Have a clear failed intubation plan and ensure you can ventilate with bag-mask and have supraglottic airway and front-of-neck access equipment available.
  • Ensure monitoring and resuscitation drugs are ready (including atropine for bradycardia, and emergency anaphylaxis kit).

Dosing and practical tips

  • Typical adult IV dose: 1–1.5 mg/kg (use local guidance; dose may be adjusted in specific scenarios).
  • Onset is rapid; intubation is often attempted at ~45–60 seconds depending on technique and patient factors.
  • Avoid repeat doses unless there is a clear reason and you understand the bradycardia risk; if repeat dosing is needed, discuss with a senior.
  • Expect fasciculations; consider that they can increase intra-abdominal/intra-gastric pressure slightly and can cause postoperative muscle aches.
  • If paralysis lasts longer than expected, consider pseudocholinesterase deficiency or drug interactions; continue ventilation and sedation until recovery and seek senior help.

What to watch for after giving it

  • Bradycardia: more common with repeat doses, children, or vagal stimulation; treat promptly (e.g., atropine per local policy).
  • Hyperkalaemia: look for ECG changes (peaked T waves, widening QRS, arrhythmias) especially in at-risk patients; treat as an emergency and call for help.
  • Anaphylaxis: sudden hypotension, bronchospasm, rash/urticaria; manage immediately per anaphylaxis guidelines and document clearly.
  • Malignant hyperthermia: rare but life-threatening; rising CO2, tachycardia, rigidity, hyperthermia later; stop triggers, call for help, give dantrolene per protocol.
  • Raised intraocular/intracranial pressure: usually avoid if open globe injury; discuss with seniors in head injury/neurosurgical contexts.
What is the main reason to choose suxamethonium?

– Fastest onset for paralysis – Short duration – Often used for RSI when speed is critical

Is suxamethonium still used for RSI now that we have rocuronium + sugammadex?

– Yes, in many places – Choice depends on patient factors, contraindications, and local practice – Rocuronium is preferred if suxamethonium is risky (e.g., hyperkalaemia risk)

What patients are at highest risk of dangerous hyperkalaemia with suxamethonium?

– Major burns (especially from ~24–48 hours after injury until healed) – Denervation/paralysis (spinal cord injury, stroke with significant weakness) – Neuromuscular disease (e.g., motor neurone disease) – Prolonged immobility/critical illness (ICU-acquired weakness) – Major crush injury or rhabdomyolysis

How soon after a burn is suxamethonium unsafe?

– Risk increases after the first day (often quoted from ~24–48 hours) – Can persist for weeks to months until recovery/healing – If in doubt: avoid and use an alternative

What should I do if suxamethonium lasts much longer than expected?

– Continue ventilation and give adequate sedation/analgesia – Consider pseudocholinesterase deficiency or drug effects – Inform a senior and document clearly; the patient may need follow-up testing

Does suxamethonium cause bradycardia?

– Yes, especially with repeat dosing and in children – Be ready to treat (e.g., atropine per local guidance) – Consider using an alternative if bradycardia risk is high

When should I avoid suxamethonium because of eye injury?

– Suspected or confirmed open globe injury: avoid (can raise intraocular pressure) – Use a non-depolarising agent instead and discuss with seniors

What are the key immediate complications to be ready for?

– Anaphylaxis – Severe bradycardia – Hyperkalaemic arrhythmia – Malignant hyperthermia (rare but critical)

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