Suxamethonium (Anaesthesia/RSI)

eMC §4.2 (Suxamethonium Chloride 50mg/ml Solution for Injection, emc product 5189): 'To achieve endotracheal intubation, Suxamethonium is usually administered intravenously in a dose of 1mg/kg.' The dose depends on body weight, the degree of muscular relaxation required, the route of administration and the response of the individual patient. The 1 mg/kg intubating dose usually produces muscular relaxation in about 30 to 60 seconds with a duration of action of about 2 to 6 minutes; larger doses produce more prolonged relaxation, but doubling the dose does not necessarily double the duration. INFUSION (prolonged surgical procedures): may be given by 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 the response of the individual patient. ELDERLY: dosage requirements are comparable to those for younger adults, but the elderly may be more susceptible to cardiac arrhythmias, especially if digitalis-like drugs are also being taken. HEPATIC IMPAIRMENT: termination of action depends on plasma cholinesterase, which is synthesised in the liver; although plasma cholinesterase levels often fall in liver disease, levels are seldom low enough to significantly prolong suxamethonium-induced apnoea. REDUCED PLASMA CHOLINESTERASE: patients may experience prolonged and intensified neuromuscular blockade, and it may be advisable to administer reduced dosages. MONITORING: monitoring of neuromuscular function is recommended during infusion, or if relatively large cumulative doses are given over a relatively short period, in order to individualise dosage requirements. ADMINISTRATION SAFETY (§4.4): suxamethonium paralyses the respiratory muscles as well as other skeletal muscles but has no effect on consciousness — it must not be given to a patient who is not fully anaesthetised, and should be administered only by or under the close supervision of an anaesthetist who is familiar with its actions, characteristics and hazards, who is skilled in the management of artificial respiration, and only where there are adequate facilities for immediate endotracheal intubation and administration of oxygen by intermittent positive pressure ventilation. PAEDIATRIC — HELD OUT OF THE STRUCTURED FIELD ON PURPOSE (see paedDose note below): §4.2 states 'Infants and young children are more resistant to suxamethonium compared with adults. 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. When Suxamethonium is given as intravenous infusion in children, the dosage is as for adults with a proportionately lower initial infusion rate based on body weight. Suxamethonium may be given intramuscularly to infants at doses up to 4 to 5mg/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.' §4.4 adds that bradycardias are more commonly observed in children, or if repeated doses are given, and that pre-treatment with intravenous atropine or glycopyrrolate can significantly reduce the incidence and/or severity of suxamethonium-related bradycardia. Verify all paediatric use against a children's formulary. SOURCE CAVEAT: the fetched §4.3 and §4.4 were both cut off at the source-fetch limit, so the contraindication and warning content below is not necessarily complete — the clinician must review the full SPC. SUPERSEDES EARLIER HOLD: a previous draft of this page (and of the identically-sourced suxamethonium-chloride page) was held because its structured paedDose published a flat 2 mg/kg with no age qualifier — the neonate/infant value, twice the labelled dose for an older child once a calculator consumes the field, and a particular risk on this RSI-badged page where a per-kg number is most likely to be acted on at speed. That defect is not repeated here: paedDose is deliberately null and both age bands are stated in full above.