Suxamethonium (Anaesthesia/RSI)

How it works

It binds and persistently activates nicotinic acetylcholine receptors at the neuromuscular junction, causing sustained depolarisation that prevents further muscle contraction.

Prescribing in practice

• Suxamethonium is a recognised trigger for malignant hyperthermia and can cause life-threatening hyperkalaemia in susceptible patients (burns, prolonged immobility, denervation, severe sepsis), so screen for these before use.
• It can cause profound bradycardia, particularly in children and with repeat doses, and is contraindicated where there is suxamethonium apnoea due to pseudocholinesterase deficiency causing prolonged paralysis.
• Because it provides only brief paralysis, a plan for ongoing airway control and ventilation must be in place before administration.

Monitoring

Monitor neuromuscular function, ECG, oxygenation, and temperature, remaining alert for hyperkalaemia, prolonged block, and signs of malignant hyperthermia.

Counselling the patient

• Warn that postoperative muscle aches (myalgia) are common after suxamethonium.
• If prolonged paralysis from pseudocholinesterase deficiency is suspected, advise the patient and family that relatives may also be affected and should be informed.
• Reassure that breathing is fully supported while the drug is working.

Evidence & guidelines

Suxamethonium remains the classic agent for rapid sequence induction in UK anaesthetic practice, with its hyperkalaemia and malignant hyperthermia risks well established in standard texts.