Final answer:
Tetracaine is the ester local anesthetic among the options provided. Lignocaine, prilocaine, and bupivacaine are considered amide local anesthetics. These drugs work by inhibiting sodium ion entry into nerves and thereby preventing pain signals.
Step-by-step explanation:
Among the local anesthetics mentioned, tetracaine is an ester local anesthetic. Local anesthetics are important medications used to prevent pain in specific areas of the body by blocking the conduction of nerve impulses. They can be structurally classified into two groups: amides and esters. Tetracaine, also known by its generic name as amethocaine, is one of the esters and is used for short procedures due to its quick onset and medium duration of action.
Other drugs listed, such as lignocaine (also known as lidocaine), prilocaine, and bupivacaine, are amide local anesthetics. They have varying durations of action and are used for various procedures. All these agents work by blocking voltage-gated sodium channels which prevent sodium ions from entering the nerve cell, thereby stopping nerve impulse conduction which leads to numbness and prevention of pain sensation.