Question

Mechanism of action of local anaesthetic

Answer 1

Local anesthetics produce anesthesia by inhibiting excitation of nerve endings or by blocking conduction in peripheral nerves. This is achieved by anesthetics reversibly binding to and inactivating sodium channels. Sodium influx through these channels is necessary for the depolarization of nerve cell membranes and subsequent propagation of impulses along the course of the nerve. When a nerve loses depolarization and capacity to propagate an impulse, the individual loses sensation in the area supplied by the nerve.

The order of affinity of local anesthetics for different sodium channel states is open is better than inactivated, which is better than resting. Thus, the open state of the sodium channel is the primary target of local anesthetic molecules. The blocking of propagated action potentials is therefore a function of the frequency of depolarization. The mechanism for differential block, the block of pain perception without motor block, is still unclear.