This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: A.N.S., Subject name: Pharmacology
[{'content': 'Esmolol is a short acting beta blocker because: \nSelect and explain. \nA. It has more plasma protein binding, B. Its plasma hydrolysis by esterases is rapid, C. It has high lipid solubility, D. It has high oral bioavailability', 'role': 'user'}, {'content': "Answer: B \nExplanation: (Ref Goodman & Gillman's 13th ed. P 216-17)Esmolol is a b1-selective antagonist with a rapid onset and a very short duration of action (t 1/2 = 8 minutes).The drug is hydrolyzed rapidly by esterase's in erythrocytes leading to its short half-life.Esmolol is used in urgent settings where immediate onset of b-blockade is warranted so it is given by slow intravenous injection.A partial loading dose (500mg/kg over 1 minute) typically is administered, followed by a continuous infusion of the drug (maintenance dose of 50mg/kg/minfor 4 minutes)The lipid solubility of esmolol is low and has no oral bioavailability so it is given via IV.The protein binding of esmolol is 55%.", 'role': 'assistant'}]