Which enzyme metabolizes ester-type local anesthetics?

Which enzyme metabolizes ester-type local anesthetics?

• A. Monoamine oxidase
• B. Pseudocholinesterase
• C. Cytochrome P450
• D. Carboxylesterase

Answer: (B)

Ester-type local anesthetics are quickly inactivated by enzymes in the blood, specifically plasma esterases. The major enzyme doing this hydrolysis is pseudocholinesterase, also known as plasma cholinesterase. This rapid breakdown shortens the duration of ester-type LAs like procaine and benzocaine. Monoamine oxidase breaks down amines, not esters. Cytochrome P450 enzymes in the liver handle many drugs, including the hepatic metabolism of amide-type local anesthetics. Carboxylesterase can hydrolyze esters in some tissues, but the classic and most direct mechanism for ester-type LAs is hydrolysis by pseudocholinesterase. Atypical deficiencies of pseudocholinesterase can lead to prolonged effects of ester-type anesthetics, highlighting why this enzyme is the key player here.

Ester-type local anesthetics are quickly inactivated by enzymes in the blood, specifically plasma esterases. The major enzyme doing this hydrolysis is pseudocholinesterase, also known as plasma cholinesterase. This rapid breakdown shortens the duration of ester-type LAs like procaine and benzocaine.

Monoamine oxidase breaks down amines, not esters. Cytochrome P450 enzymes in the liver handle many drugs, including the hepatic metabolism of amide-type local anesthetics. Carboxylesterase can hydrolyze esters in some tissues, but the classic and most direct mechanism for ester-type LAs is hydrolysis by pseudocholinesterase.

Atypical deficiencies of pseudocholinesterase can lead to prolonged effects of ester-type anesthetics, highlighting why this enzyme is the key player here.