How do ester local anesthetics differ from amide local anesthetics?

• A. Ester anesthetics are metabolized by the liver
• B. Amide anesthetics have a longer duration
• C. Ester anesthetics are more potent
• D. Amy de anesthetics are metabolized by plasma cholinesterase

Answer: (B)

Ester and amide local anesthetics differ primarily in their chemical structure and how they are metabolized in the body. One significant reason that amide anesthetics tend to have a longer duration compared to ester anesthetics is because of the differences in their metabolic pathways.

Amide anesthetics, such as lidocaine and bupivacaine, are primarily metabolized in the liver by hepatic enzymes. This metabolism is generally more robust and slower, leading to a prolonged effect, especially in cases where there’s extended therapeutic use or when the anesthetic is administered in larger doses. Their pharmacokinetics allow for a longer duration of action due to slower breakdown, which increases the potential for sustained anesthetic effects.

In contrast, ester anesthetics, like procaine and cocaine, are typically metabolized in the plasma by the enzyme pseudocholinesterase, which leads to a quicker breakdown. This fast metabolism results in a shorter duration of effect, making ester anesthetics suitable for procedures that do not require prolonged anesthesia.

Therefore, the characteristic of amide anesthetics having a longer duration of action due to their metabolic processes sets them apart from ester anesthetics, making the choice regarding their duration accurate and relevant in the context of local anesthesia.