Which of the following local anesthetics has an amide linkage?

Lidocaine is the correct choice because it contains an amide linkage within its chemical structure. In local anesthetics, the type of linkage—either ester or amide—plays a critical role in determining the metabolic pathway and duration of action. Amide local anesthetics, like lidocaine, are generally more stable and have a longer duration of action than their ester counterparts. They are metabolized primarily in the liver and have a lower risk of allergy due to their metabolic process.

In contrast, procaine, cocaine, and benzocaine are examples of local anesthetics that contain ester linkages. Esters are known for their rapid metabolism, which often leads to shorter durations of action and a higher likelihood of inducing allergic reactions in some patients. Understanding the structural differences between these classes of local anesthetics is essential for effective clinical practice and safe patient management.