Dose and Administration

1. 1-2 mg/kg/dose slow IV injection or 2 mg/kg/dose IM.

Indication

1. Short duration muscle relaxation to facilitate intubation.

Contraindications and Precautions

1. Known hypersensitivity to suxamethonium chloride.
2. Known or suspected deficiency of plasma pseudocholinesterase.
3. Family history of malignant hyperthermia.
4. Hyperkalaemia.
5. Caution in preterm infants, especially extreme immaturity.
6. Caution in neonates with renal impairment.
7. Caution in neonates with cardiac arrhythmias.
8. Caution in neonates with congenital myopathy.

Clinical Pharmacology

Suxamethonium chloride (also known as succinylcholine) is a depolarising muscle relaxant. Action due to initial stimulation then prolonged depolarisation of receptors for acetylcholine at the neuromuscular junction. Suxamethonium may have a number of effects apart from skeletal muscle relaxation (hyperkalaemic response, cardiac arrhythmias).

Poorly absorbed from gastrointestinal tract - must be given IM or IV. Rapidly and completely hydrolysed by hepatic and plasma pseudocholinesterase. Very rapid onset of action (1-2 minutes). Continuous administration over a prolonged period of time may result in irreversible blockage (phase II block). Short duration of action: 3-5 minutes (with IM administration may be prolonged 10-15 minutes).

Possible Adverse Effects

1. Bradycardia
2. Hyperkalaemia
3. Prolonged paralysis
4. Phase II (dual) block
5. Hypersensitivity reactions
6. Malignant hyperthermia

Special Considerations

1. See Intubation Protocol.
2. Should not be used without additional sedation.
3. Bradycardia common in neonates and children, especially after a second dose of suxamethonium. May be prevented by administration of atropine 20 mcg/kg prior to administration of suxamethonium.
4. Suxamethonium causes a transient rise in serum potassium. Usually not a problem unless serum potassium already very high, or potassium release is enhanced.
5. Deficiency of pseudocholinesterase may be genetic or acquired. Incidence approximately 1:2000 in adult population.
6. Management of suxamethonium overdose and/or toxicity is supportive (ventilation, insulin glucose infusion for hyperkalaemia, antiarrhythmic agents).