Depolarizing Neuromuscular Blocking Agents

• Overview:  Succinylcholine (Anectine)

  • Very brief duration of action (5-10 minutes)

  • Brief duration of action due to: rapid hydrolysis by plasma cholinesterase (butrylcholinesterase/pseudocholinesterase).

    •  Extended duration of action would occur with reduced plasma cholinesterase activity.

  • Initial metabolite of succinylcholine (Anectine): succinylmonocholine (very weak neuromuscular blocking effect).

  • Termination of pharmacological effect--diffusion away from postsynaptic receptors (note the absence of pseudocholinesterase at post-junctional sites).

•  Genetic variation: effects on duration of action of succinylcholine (Anectine) blockade

  • Abnormal plasma cholinesterase may prolong succinylcholine (Anectine) effects

  • "Dibucaine (Nupercainal, generic)-number" test identifies patients with abnormal plasma cholinesterase (dibucaine (Nupercainal, generic) inhibits the "normal" enzyme by 80% & the abnormal enzyme by only 20%).

    •  Dibucaine (Nupercainal, generic)-variants are the most common plasma cholinesterase genetic variants.