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Suxamethonium 💊
Related Subjects: |Respiratory Failure |Non invasive ventilation (NIV) |Intubation and Mechanical Ventilation |Critical illness neuromuscular weakness |Haemodialysis |Dobutamine
💉 Suxamethonium (succinylcholine) is the classic depolarising muscle relaxant used for rapid sequence induction (RSI). It has a very rapid onset and short duration of action, making it ideal for airway control in emergencies. ⚠️ However, its use carries important risks including hyperkalaemia, malignant hyperthermia, and suxamethonium apnoea.
📖 About
- Always check the BNF link here for up-to-date prescribing advice.
- Depolarising neuromuscular blocker, metabolised by plasma pseudocholinesterase.
⚙️ Mode of Action
- Binds to the nicotinic acetylcholine receptor at the neuromuscular junction → persistent depolarisation → paralysis.
- Not broken down by acetylcholinesterase at the synapse, leading to sustained block.
- Metabolised by plasma pseudocholinesterase in the circulation.
💊 Indications/Dose
| Name | Starting Dose | Frequency | Route |
|---|---|---|---|
| Suxamethonium | 1.5–2 mg/kg | Single dose | IV |
⏱️ Action
- Fasciculations in 5–15 seconds.
- Complete paralysis in 45–60 seconds.
- Return of spontaneous breathing: 5–10 minutes.
🔗 Interactions
- See BNF for full list (interactions with anaesthetic agents, certain antibiotics, and anticholinesterases).
⚠️ Cautions
- Raises serum potassium by ~0.5 mmol/L → dangerous in patients with baseline hyperkalaemia.
- Use with caution in renal failure, neuromuscular disorders, burns, severe trauma, or sepsis.
- Bradycardia more likely in children and with repeated doses.
⛔ Contraindications
- Known pseudocholinesterase deficiency (risk of prolonged apnoea).
- Hyperkalaemia or conditions predisposing to it (burns, cord injury, severe sepsis, crush injuries).
- Personal or family history of malignant hyperthermia.
💥 Side Effects
- Hyperkalaemia and risk of cardiac arrest.
- Bradycardia, especially in children.
- Muscle fasciculations and postoperative myalgia.
- Histamine release → flushing, bronchospasm, hypotension.
- Malignant hyperthermia (rare but life-threatening).
- Suxamethonium apnoea: prolonged paralysis in patients with pseudocholinesterase deficiency.
📚 References
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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