Pharmacodynamics Esmolol is a
beta blocker, or an
antagonist of the
β-adrenergic receptors. one that is rapidly metabolized to an inactive form. Esmolol is rapidly metabolized by hydrolysis of the ester linkage, chiefly by the esterases in the cytosol of red blood cells and not by plasma cholinesterases or red cell membrane acetylcholinesterase. Total body clearance in man was found to be about 20 L/kg/hr, which is greater than cardiac output; thus the metabolism of esmolol is not limited by the rate of blood flow to metabolizing tissues such as the liver or affected by hepatic or renal blood flow. Esmolol's short duration of action is based on the
ester-
methyl side chain which allows for quick hydrolysis. Esmolol's structure is reflected in its name,
es-molol as in
ester-
methyl. Plasma cholinesterases and red cell membrane acetylcholinesterase do not have any action. This metabolism results in the formation of a free acid and
methanol. The amount of methanol produced is similar to endogenous methanol production. Esmolol has a rapid distribution half-life of about two minutes and an elimination half-life of about nine minutes. Esmolol is classified as a beta blocker with moderate
lipophilicity and hence moderate potential for crossing the
blood–brain barrier. As such, esmolol may produce effects in the
central nervous system and have a risk of
neuropsychiatric side effects. ==Chemistry==