SUXAMETHONIUM

“SCOLINE”

1) Action

• Depolarising muscle relaxant

• Ultra short acting muscle relaxant

2) Mechanism

• This drug is 2 molecules of Ach linked together which depolarises the motor end plates

• Similar action to Ach except producers a longer effect; as it is not metabolised as rapidly as Ach, the depolarised membranes remain depolarised and unresponsive to additional stimuli

3) Indications

• Total but brief relaxation for intubation or eg oesophagoscopy

• Always used for intubation when patient has a full stomach as action is so rapid and relaxation is complete

4) Effects on organs—side effects

• Stimulates all autonomic cholinoceptors [stimulates cardiac muscarinic receptors]

• Initial bradycardia and hypotension from vagal stimulation

• Bradycardia [treat with atropine]

• Hyperkaelemia: releases potassium from muscles

5) Toxic effects/ precautions with administration

• Prolonged effect due to congenital abnormal pseudocholinesterase

6) Contraindications

• Caution in patients with preexisting hyperkalaemia &/or extensive tissue injury/burns

7) Reversal, antagonism or antidote

• No pharmacological antidote: artificial respiration until effects wear off

8) Loading dose, maintenance dose, frequency & method of administration

• 50mg/ml ampoules [2 ml]

• 1mg/kg weight

• Unstable drug: stored in fridge

9) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• 5—10 minutes duration of action

• Elimination half life: 2 min

• Suxamethonium is destroyed within several minutes by circulating pseudocholinesterase

10) Important drug interactions

• Caution with digoxin as may exacerbate vagal effects