NMJ Blocking Agents

What is the prototype for nondepolarizing NMJ blockers?

Pancuronium

• Others include cisatracurium, rocuronium, and vecuronium

What is the action of pancuronium?

Occupies muscle cholinergic receptor sites preventing ACh from reacting with the receptors, so muscle cells are not activated and flaccid paralysis occurs

What is the indication for pancuronium?

Muscle paralysis is required or desired

What are the CI for pancuronium?

Myasthenia gravis, renal or hepatic disease, and pregnancy

What are the cautions for pancuronium? 

History of malignant hyperthermia, pulmonary or cardiac dysfunction, F&E imbalance, respiratory disease, and lactation

What are the AE of pancuronium?

Mostly related to muscle paralysis

• Histamine release occurs (i.e., wheezing, bronchospasm, etc.)

• Hypotension/cardiac arrhythmias

• GI effects

• Hyperkalemia

What are the DI for pancuronium?

• Volatile liquids, aminoglycoside ABXs, and CCBs increase paralysis

• Cholinesterase inhibitors decrease the effectiveness

• Xanthines reverse the paralysis

• Barbiturates could cause a precipitate to form

What are the herb interactions for pancuronium?

Melatonin and valerian increase sedation/paralysis and slow recovery

What is the prototype for depolarizing NMJ blockers?

Succinylcholine

• Only one in drug class

What is the action of succinylcholine?

Attaches to ACh receptors on muscle cells, prolonging depolarization of the muscle (i.e., muscle stimulation/contraction occurs), followed by flaccid paralysis

• Basically, a massive and prolonged depolarization/muscle contraction occurs, so the muscle stops responding to stimuli

What is the indication for succinylcholine?

Muscle paralysis is required or desired

What is the CI for succinylcholine?

Conditions causing low plasma cholinesterase levels

What are the cautions for succinylcholine?

Fractures, eye considerations, and paraplegia or SCI

What are the AE of succinylcholine?

Same as nondepolarizing NMJ blockers (i.e., mostly related to muscle paralysis, histamine release occurs, hypotension/cardiac arrhythmias, hyperkalemia, and GI)

• Muscle pain

• Malignant hyperthermia

What are the DI for succinylcholine?

Same as nondepolarizing NMJ blockers (i.e., volatile liquids, aminoglycoside ABXs, CCBs, cholinesterase inhibitors, xanthines, and barbiturates)

• Cholinesterase inhibitors increase the effects of succinylcholine