Local anesthetics are medications used to block pain sensation in a specific part of the body, in order to perform small surgical procedures.
There are 2 classes of local anesthetics; esters; and amides. Both of these types block the sodium channels in the peripheral nerves, and inhibit the conduction of action potentials across nerve fibers. Thus, they inhibit the perception of pain by the brain.

Pain is sensed by receptors called free nerve endings, which are the first order neurons in the pain pathway. These neurons can be stimulated in several ways. By mechanical stimulation; thermal stimulation, such as heat and cold; chemical stimulation by molecules, like bradykinin and histamine.

These stimuli trigger the opening of transient receptor potential channels on the membrane of free nerve endings. This allows sodium and other cations to flow into the cell, causing dee polarization. This will result in opening of the nearby voltage gated sodium channels, setting off the positive membrane potential that continues down the entire length of the axon.

Local anesthetics bind to the voltage gated sodium channels intra cellularly in their inactivated state. By binding, they prolong the inactivation state of the channel, which prevents propagation of the action potentials. Local anesthetics have a greater effect on small and myelinated nerve fibers. At larger doses, they can block temperature, touch, and pressure sensation as well.



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