Final answer:
Lidocaine, a local anesthetic, takes effect in 3 to 5 minutes, functioning by blocking Na+ channels, which prevents nerve impulse transmission, causing numbness and pain relief.
Step-by-step explanation:
Lidocaine's Mechanism of Action and Onset Time:
Lidocaine, the most widely used local anesthetic, takes effect in 3 to 5 minutes and is effective for 60 to 90 minutes. This drug, like novocaine, acts as a Na+ channel blocker. By preventing sodium ions from moving across the neuronal membrane, lidocaine inhibits the generation and propagation of nerve impulses. When lidocaine is applied to the skin or injected locally, it can prevent the initiation and transmission of sensory impulses, leading to numbness and pain relief in a specific area. Despite the temporary discomfort of the injection, the absence of it would result in a much more unpleasant experience due to unmitigated pain. The primary reason lidocaine is such an effective local anesthetic is because nerve conduction can be selectively and reversibly interrupted, causing sensory and sometimes motor paralysis without structural damage to nerve fibers or cells.