A Brief Review of Neuromuscular Blocking Agents
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Skeletal Muscle relaxants
Mechanism of action
1. Succinylcholine caused initial activation of the muscle AchR followed by desensitization
2. At clinically relevant concentrations, succinylcholine has no stimulatory or inhibitory interactions with α3β2 (presynaptic) or α3β4 (ganglionic) AchRs
3. High doses of succinylcholine caused inhibition of both α3β2 and α3β4 receptor.
Pharmacokinetics of neuromuscular blocking drugs
Approximate duration of action (minutes)
Approximate potency relative to Tubocurarine
Kidney (60%) and liver
Liver (75-90%) and kidney
Plasma ChE (100%)
Soutce: Bertram G. Katzung, Susan B. Masters and Anthony J. Trevor. Basic amd Clinical Pharmacology. 11th Edition. Chapter 27. Skeletal Muscle Rexants. Page 451-465.
Pharmacology of Neuromuscular blocking drugs
Intubating dose (mg/kg)
Onset timeb (s)
a: The dose that depresses the twitch height by 95%
b: time to 95% depression of first twitch of train-of-four
c: time to 25% recovery of first twitch of train-of-four
d: This is about three times the ED95
Source: Jonnas Appiah-Ankam, Jennifer M Hunter. Pharmacology of neuromuscular blocking drugs. Contin Educ Anaesth Crit Care Pain. 2004;4(1):2-7.
Side effects of succinylcholine: (2)
Effects of muscle relaxants:
Effect on autonomic ganglia
Effect on cardiac muscarinic receptors
Tendency to cause histamine release
Source: Bertram G. Katzung, Susan B. Masters and Anthony J. Trevor. Basic amd Clinical Pharmacology. 11th Edition. Chapter 27. Skeletal Muscle Rexants. Page 451-465.
Interactions with other drugs
Isoflurane (most); sevoflurane, desflurane, enflurane and halothane; nitrous oxide (least)
Reversal of nondepolarizing neuromuscular blockade