Which anesthetic is not an amide?

• A. Procaine
• B. Lidocaine
• C. Mepivacaine
• D. Bupivacaine

Answer: (A)

Local anesthetics are grouped by the chemical bond between the aromatic ring and the amine group: amide bonds or ester bonds. This structural difference changes how the drug is broken down in the body. Esters are rapidly hydrolyzed by plasma cholinesterases, which generally gives a shorter duration of action and a higher potential for hypersensitivity related to the PABA metabolite. Amides, on the other hand, are more stable in blood and are mainly metabolized in the liver, often resulting in a longer-lasting effect.

The anesthetic that is not an amide is the one with an ester linkage. It is rapidly broken down by plasma cholinesterases, leading to a shorter duration. The other three are amides, metabolized in the liver, and typically provide a longer duration of anesthesia.