<prompt> Wof agents is often combined with local anesthetics to prevent its systemic distribution from the site of injectionAcetylcholineDopamineEpinephrineg-Aminobutyric acid GABA  <response>: 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 