This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia, Subject name: Pharmacology
[{'content': 'Wof agents is often combined with local anesthetics to prevent its systemic distribution from the site of injection \nSelect and explain. \nA. Acetylcholine, B. Dopamine, C. Epinephrine, D. g-Aminobutyric acid (GABA)', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 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', 'role': 'assistant'}]