Suxamethonium (Succinylcholine)

Dose depends on body weight, degree of muscular relaxation required, route of administration and individual response. Larger doses produce more prolonged relaxation, but doubling the dose does not necessarily double the duration. PROLONGED PROCEDURES — intravenous infusion as a 0.1% to 0.2% solution, diluted in 5% glucose solution or sterile isotonic saline solution, at a rate of 2.5 to 4 mg per minute, adjusted according to individual response. Monitoring of neuromuscular function is recommended during infusion or when relatively large cumulative doses are given over a short period. ELDERLY — dosage requirements comparable to younger adults; the elderly may be more susceptible to cardiac arrhythmias, especially if digitalis-like drugs are also being taken. REDUCED PLASMA CHOLINESTERASE — prolonged and intensified neuromuscular blockade may occur; it may be advisable to administer reduced dosages. HEPATIC IMPAIRMENT — plasma cholinesterase levels often fall in liver disease but are seldom low enough to significantly prolong suxamethonium-induced apnoea. Suxamethonium paralyses respiratory muscles and has no effect on consciousness; administer only by or under close supervision of an anaesthetist, with facilities for immediate endotracheal intubation and intermittent positive pressure ventilation. Pre-treatment with intravenous atropine or glycopyrrolate can significantly reduce suxamethonium-related bradycardia. NOTE ON SOURCES: §4.5 was not captured in the fetched bundle — the interactions listed are taken from the §4.3/§4.4 text that was captured; clinician to check the full §4.5.

The SPC gives two age-band intravenous doses, so no single per-kg value can be entered: 'The recommended intravenous dose of Suxamethonium for neonates and infants is 2 mg/kg. A dose of 1 mg/kg in older children is recommended.' Infants and young children are more resistant to suxamethonium compared with adults. INTRAMUSCULAR: 'Suxamethonium may be given intramuscularly to infants at doses up to 4 to 5 mg/kg and in older children up to 4 mg/kg. These doses produce muscular relaxation within about 3 minutes. A total dose of 150 mg should not be exceeded.' Bradycardias are more commonly observed in children. There are case reports of hyperkalaemia-related cardiac arrest following suxamethonium in patients with congenital cerebral palsy, tetanus, Duchenne muscular dystrophy and closed head injury, and rarely in children with hitherto undiagnosed muscular disorders. Verify against a children's formulary before use.