The primary mechanism by which the action of tetracaine is terminated when used for spinal anesthesia is

The primary mechanism by which the action of tetracaine is terminated when used for spinal anesthesia is

• A. Systemic absorption
• B. Uptake into neurons
• C. Hydrolysis by pseudocholinesterase
• D. Hydrolysis by nonspecific esterases

Answer: (A)

Termination of tetracaine’s spinal block is determined mainly by systemic absorption from the intrathecal space. As the drug diffuses into surrounding tissues and is taken up into the bloodstream, its concentration around the nerve roots drops, reducing the blockade below the level needed to maintain Na⁺ channel inhibition. Metabolism after it reaches the blood (such as hydrolysis by plasma cholinesterases) occurs, but it’s not the primary step that stops the block in the spinal space. Uptake into neurons describes the mechanism of action rather than termination, and while ester hydrolysis contributes to elimination, the rate‑limiting event for ending the spinal anesthesia is the drug’s systemic absorption.

Termination of tetracaine’s spinal block is determined mainly by systemic absorption from the intrathecal space. As the drug diffuses into surrounding tissues and is taken up into the bloodstream, its concentration around the nerve roots drops, reducing the blockade below the level needed to maintain Na⁺ channel inhibition. Metabolism after it reaches the blood (such as hydrolysis by plasma cholinesterases) occurs, but it’s not the primary step that stops the block in the spinal space. Uptake into neurons describes the mechanism of action rather than termination, and while ester hydrolysis contributes to elimination, the rate‑limiting event for ending the spinal anesthesia is the drug’s systemic absorption.