Nondepolarizing Neuromuscular-blocking Drugs

Summary

The nondepolarizing neuromuscular junction blockers like atracurium and rocuronium are curare-derivatives used in anesthesia for paralysis during surgery. These agents act by competitively blocking nicotinic receptors, postsynaptically at the neuromuscular junction. This prevents depolarization and inhibits muscle contraction. Train of Four stimulation will show progressive reduction of muscle response. Neostigmine is the drug of choice to reverse these agents, and don’t forget the hypotension and respiratory depression are seen as possible side effects.

Key Points

• Nondepolarizing Neuromuscular Blocking Drugs
  • Curare-derivatives
    • -curarine (Tubocurarine, Rubocurarine)
    • -curium (Atracurium, Mivacurium)
    • -curonium (Pancuronium, Vecuronium, Rocuronium)
  • Mechanism of Action
    • Competitive ANTAGONIST at nicotonic receptors in skeletal muscle
      • → prevent depolarization (hence, non-depol)
  • Clinical Use
    • Induction of anesthesia in a surgical procedure
    • Used to provide muscle relaxation and diminish reflexes
      • Train of four (TOF) stimulation (electrical stimulation of peripheral nerve) will show a progressive reduction (fading pattern)
        • TOF is used during anesthesia to assess the degree of paralysis induced by NMJ-blocking agents
  • Reversal
    • Acetylcholinesterase inhibitor reversal (neostigmine, edrophonium)
      • Administer with atropine to prevent off-target muscarinic effects (e.g. bradycardia)
  • Adverse Effects
    • Hypotension
    • Respiratory depression