Long-acting nondepolarising NMBDs

[SH4:p228-231]

• Pancuronium is the most commonly used long-acting nondepolarising NMBDs
• Doxacurium and pipecuronium are like pancuronium
  * But does not have CVS side effects like pancuronium

Doxacurium

• A benzylisoquinolinium nondepolarising NMBD
• ED95 = 30mcg/kg
  * c.f. pancuronium's ED95 = 70mcg/kg
• Intubating dose = 0.05 mg/kg
  * [CEACCP 2004 Vol 4(1) "Pharmacology of neuromuscular blocking drugs"]
• Onset of action = 4-6 minutes
  * Slow
  * c.f. pancuronium 3-5 minutes
• Duration of NMJ blockade = 60-90 minutes
  * Long
  * Same as pancuronium
• Does not have CVS effects like pancuronium
  * No histamine release

Pipecuronium

• A bisquaternary aminosteroid nondepolarising NMBD
• ED95 = 50mcg/kg
• Onset of action = 3-5 minutes
• Duration of NMJ blockade = 60-90 minutes
• But hepatic cirrhosis does not seem to alter the pharmacokinetics or pharmacodynamics of pipecuronium

Pipecuronium vs pancuronium

• Pipecuronium was similar to pancuronium in:
  * Structure
  * Pharmacokinetics (e.g. onset of action and duration)
  * Dependence on renal clearance
• In contrast to pancuronium, pipecuronium was:
  * More potent
  * No vagolytic or sympathomimetic effects

Tubocurarine

[CEACCP 2004 Vol 4(1) "Pharmacology of neuromuscular blocking drugs"]

• Long onset of action
• Prolonged duration
• Marked histamine release
  --> Pronounced hypotension and tachycardia
• In large doses
  --> May produce ganglion block