Wof agents is often combined with local anesthetics to prevent its systemic distribution from the site of injection

Addition of a vasoconstrictor, e.g. adrenaline (1:50,000 to 1:200,000): * Prolongs duration of action of LAs by decreasing their rate of removal from the local site into the circulation: contact time of the LA with the nerve fibre is prolonged. * Enhances the intensity of nerve block. * Reduces systemic toxicity of LAs: rate of absorption is reduced and metabolism keeps the plasma concentration lower. * Provides a more bloodless field for surgery. * Increases the chances of subsequent local tissue edema and necrosis as well as delays wound healing by reducing oxygen supply and enhancing oxygen consumption in the affected area. Ref:- kd tripathi; pg num:-363