What is an important difference in metabolism between ester and amide local anesthetics?

• A. Ester local anesthetics are metabolized by liver enzymes
• B. Amide local anesthetics are hydrolyzed by plasma cholinesterase
• C. Ester local anesthetics are hydrolyzed by plasma cholinesterase
• D. Amide local anesthetics are eliminated by the kidneys

Answer: (C)

Ester local anesthetics are primarily metabolized through hydrolysis in the plasma, and this process is facilitated by enzymes known as plasma cholinesterases. This enzymatic action is crucial because it allows for a rapid breakdown of ester anesthetics, which is significant for their pharmacokinetics and duration of action.

On the other hand, amide local anesthetics are mainly metabolized in the liver through hepatic enzymes, leading to a difference in their metabolism compared to esters. While both types of anesthetics may undergo renal elimination, the key differentiator is that esters are specifically hydrolyzed by plasma cholinesterase. This distinction is fundamental in clinical settings, as it affects the choice of anesthetic based on patient factors such as liver function and the desired duration of anesthesia.