Suxamethonium

neuromuscular agent 5

1. Suxamethonium Brief presentation

2. 3/9/2013 2 Uses Wherever rapid and profound neuromuscular blockade is required Eg. To facilitate tracheal intubation For modification of fits after electroconvulsive therapy

3. Chemical The dicholine ester of succinic acid{ equivalent to 2 acetylcholine molecules joined back to back} Presentation As a clear aqueous solution containing 50mg/ml of Suxamethonium chloride The preparation should be stored at 4 degree C 3/9/2013 3

4. Main action & MOA Neuromuscular blockade of brief duration in skeletal muscle Suxamethonium causes prolonged depolarization of skeletal muscle fibers to a membrane potential above which an action potential can be triggered 3/9/2013 4

5. Route of administration and doses The intravenous dose is 0.5- 2.0 mg/kg The onset of action occurs with in 30 sec and duration of action is 3-5 min The intramuscular dose is up to 2.5mg/kg The drug may also administered sublingually at a doses of 2mg/kg 3/9/2013 5

6. Cardiovascular effects With repeated doses of sux, bradycardia and slight increase in MAP may occur Premedication with atropine Caution using on the patient already taking B-blockers 3/9/2013 6

7. Central nervous system effects The adm . Of sux may initially cause fasciculation which are then followed by phase I depolarizing block The characteristics of the block is A well sustained tetanus during stimulation at 50 -100hz The absence of post- tetanic fasciculation A train of four ratio > 0.7 and Potentiation by anticholinesterases 3/9/2013 7

8. With repeated administration or a large total dose, phase II block may develop The characteristics of this block is A poorly sustained tetanus A post tetanic fasciculation A train of four ratio < 0.3 Reversal by anticholinesterases and Tachyphylaxis 3/9/2013 8

9. Other effects ICP and IOP are both raised following administration of sux The intragastric pressure increases by 7-12cmH2O, the lower esophageal sphincter tone simultaneously decreases with the use of suxamethonium Serum potassium concentration is briefly increased in normal individual by 0.2-0.4mmol/l 3/9/2013 9

10. Toxicity & side effects Bradycardia & other dysarrythmia Hyperkalemia Postoperative myalgia – in women middle age Increases IOP,ICP & IGP Triggering agent for malignant hyperthermia Sux apnea Anaphylactic reaction 3/9/2013 10

11. Metabolism The drug is hydrolyzed by plasma cholinesterase to succinylmonocholine {which is weakly active} and choline The former is further hydrolyzed by plasma cholinesterase to succinic acid and choline 80% of administered dose is hydrolyzed before it reaches the NMJ 3/9/2013 11

12. Special points The incidence of muscle pain after administration of suxamethonium may be decreased by pre-treatment with A low dose {0.2mg/kg} dose of sux A small dose of a non-depolarizing relaxants Diazepam Aspirin or Vitamin C 3/9/2013 12

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