The action of succinylcholine at the neuromuscular junction is terminated by which mechanism?

The action of succinylcholine at the neuromuscular junction is terminated by which mechanism?

• A. Hydrolysis by pseudocholinesterase
• B. Hydrolysis by acetylcholinesterase
• C. Reuptake into nerve tissue
• D. Diffusion into extracellular fluid

Answer: (D)

Succinylcholine’s brief action is due to rapid enzymatic inactivation in the plasma by pseudocholinesterase (also known as butyrylcholinesterase). This enzyme quickly hydrolyzes the molecule into inactive metabolites, so the drug is cleared from the neuromuscular junction long before it can be reabsorbed or reuptaken or require any receptor unbinding step. Acetylcholinesterase at the junction doesn’t efficiently hydrolyze succinylcholine, so that pathway isn’t responsible for termination. Diffusion away from the receptor contributes to clearance, but it is the plasma enzymatic breakdown that mainly ends the effect. Keep in mind that genetic variants of pseudocholinesterase can prolong the duration by slowing this metabolism.

Succinylcholine’s brief action is due to rapid enzymatic inactivation in the plasma by pseudocholinesterase (also known as butyrylcholinesterase). This enzyme quickly hydrolyzes the molecule into inactive metabolites, so the drug is cleared from the neuromuscular junction long before it can be reabsorbed or reuptaken or require any receptor unbinding step. Acetylcholinesterase at the junction doesn’t efficiently hydrolyze succinylcholine, so that pathway isn’t responsible for termination. Diffusion away from the receptor contributes to clearance, but it is the plasma enzymatic breakdown that mainly ends the effect. Keep in mind that genetic variants of pseudocholinesterase can prolong the duration by slowing this metabolism.