Which tissue metabolizes ester local anesthetics?

• A. Plasma cholinesterases
• B. Liver
• C. Kidney
• D. Intestines

Answer: (A)

Esters are rapidly inactivated by hydrolysis in the bloodstream, carried out by plasma cholinesterases (pseudocholinesterase) present in circulating blood. This enzymatic activity in plasma is the primary way ester local anesthetics are metabolized, leading to a short duration of action. The liver handles amide local anesthetics, not esters, while the kidney and intestines play only minor roles in their metabolism. Variants in cholinesterase levels can slow hydrolysis and prolong effects, which is a clinically important consideration.