What is the mode of action of local anesthetics?

Sodium channels are membrane bound proteins that are composed of one large and subunit through which Na ions pass, and one or two smaller b subunits. Voltage - gated Na channels exist in three stages - resting, open and inactivated local anesthetics bind a specific region of the & subunit and inhibit voltage - gated Na channels preventing channel activation and Na influx associated with membrane depolarization. Main mechanism of action of local anesthetics is through inhibition ofActivated, voltage-gated Na channel. Local anesthetics have a greater affinity for the channel in the open or inactivated state than in the resting state. Local anesthetic binding to open or inactivated channels, or both, is facilitated by depolarization. The fraction of Na channels that have bound a local anesthetic increases with frequent depolarization (eg, during trains of impulses).This phenomenon is termed use-dependent block Local anesthetic inhibition is both voltage and frequency dependent, and is greater when nerve fibers are firing rapidly than with infrequent depolarizations Sodium passess through voltage gated sodium channel and cause change in membrane potential and cause depolarization. Local anesthetic attaches to sodium channel and prevents propogation & depolarization