neuromuscular agent 5

1. Suxamethonium
Brief presentation

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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
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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
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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
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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
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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
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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
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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
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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 reaction1/27/2019 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
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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
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