Identify the drug from the list that is NOT classified as an amide.

Procaine is the drug that is not classified as an amide; rather, it is classified as an ester. The key difference between amide and ester local anesthetics lies in their chemical structure. Amides, such as lidocaine, mepivacaine, and carbocaine, contain a specific amide linkage in their molecular structure, which affects their metabolism and duration of action. Amides are typically metabolized in the liver and tend to have a longer duration of action.

In contrast, esters like procaine are metabolized more quickly by plasma esterases, leading to a shorter duration of anesthesia. This distinction is crucial for understanding the pharmacokinetics and clinical use of local anesthetics in dental practice. Therefore, recognizing procaine as an ester clarifies its different properties compared to the amide class of anesthetics.