Which of the following is not classified as an amide?

Procaine is the correct answer as it is classified as an ester local anesthetic rather than an amide. This distinction is important in local anesthesia because esters and amides have different properties, metabolic pathways, and potential allergic reactions.

Amides, such as lidocaine and mepivacaine, are typically characterized by their longer duration of action, lower tendency to induce allergic reactions, and metabolic processing in the liver. They usually contain an amide linkage in their chemical structure. In contrast, esters like procaine are hydrolyzed by plasma pseudocholinesterase, which can lead to a shorter duration of action and a higher likelihood of allergic reactions due to the accumulation of metabolites.

Carbocaine, also known as mepivacaine, is an amide, further emphasizing the differences in classification between these types of local anesthetics. Understanding these classifications helps in clinical settings, especially when selecting the appropriate anesthetic for patient care.