Anesthesia Pharmacology: Neuromuscular Blocking Agents and Muscle Relaxants
Depolarizing Neuromuscular Blocking Agents
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).
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.