Esmolol is a short acting beta blocker because:

(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%.