Which of the following local anesthetics is considered a long-acting agent?

Bupivacaine is recognized as a long-acting local anesthetic due to its distinctive pharmacokinetic properties. It has a relatively high lipid solubility, which allows it to more effectively penetrate nerve membranes and remain bound to sodium channels for extended periods. As a result, bupivacaine provides prolonged analgesia, making it suitable for procedures that require longer durations of anesthesia, such as in surgical applications or postoperative pain management.

In contrast, other local anesthetics like lidocaine, prilocaine, and cocaine have shorter durations of action. Lidocaine is commonly used for its rapid onset and relatively short duration, while prilocaine, although slightly longer-acting than lidocaine, is still considered intermediate in action. Cocaine is notable for its historical and clinical use but has a limited duration of action and is primarily used for specific procedures, such as nasal and throat surgeries, due to its vasoconstrictive properties.

Thus, bupivacaine stands out as the agent that offers extended and sustained anesthesia, making it the correct choice when identifying a long-acting local anesthetic.