Which of the following drug(s) is/are mainly metabolized extra hepatically in plasma?
Correct Answer: Atracurium
Description: Ans. is 'd' i.e., AtracuriumoThe principal site for the metabolism of propofol is the liver.oHalothane is metabolized in the liver primarily by CYP2E1, and to a lesser extent by CYP3A4 and CYP2A6oLidocaine is about 95% metabolized (dealkylated) in the liver mainly by CYP3A4oThe unique feature of atracurium is inactivation in plasma by spontaneous nonenzymatic degradation (Hofman elimination) in addition to that by alkaline ester hydrolysis.PropofoloThe principal site for the metabolism of propofol is the liver. However, the total body clearance of propofol is greater than the generally accepted hepatic blood flow and significant extrahepatic metabolism also occur in lungs, and excreted via kidney. Metabolic clearance of propofol by the kidneys accounts for almost one-third of total body clearance and may be the major contributor to the extra-hepatic elimination of this drug.HalothaneoHalothane is an inhalational anesthetic. Most of the inhaled anesthetics are eliminated from lung, though some metabolism in liver may occur. In terms of extent of hepatic metabolism, the rank of order is methoxyflurane (>50%) > Halothane (20%)> Ether (10-15%)> enflurane (3-5%)> Sevoflurane (3%)> Isoflurane (0.2%)> desflurane (<0.1%)>N2 O(0%). N2 O does not have any metabolism in the body.oHalothane is metabolized in the liver primarily by CYP2E1, and to a lesser extent by CYP3A4 and CYP2A6 LignocaineoLidocaine is about 95% metabolized (dealkylated) in the liver mainly by CYP3A4 to the pharmacologically active metabolites monoethylglycinexylidide (MEGX) and then subsequently to the inactive glycine xylidide. Lignocaine clearance is reduced in patients with liver disease and appears to be a sensitive index of liver dysfunction.AtracuriumoThe unique feature of atracurium is inactivation in plasma by spontaneous non-enzymatic degradation (Hoffman elimination) in addition to that by alkaline ester hydrolysis. Consequently its duration of action is not altered in patients with hepatic/renal insufficiency or hypodynamic circulation - Preferred muscle relaxant for such patients as well as for neonates and the elderlyoThe major degradation product is laudanosine. Metabolites can be considered as pharmacologically inactive with the usual doses of atracurium. Because of spontaneous degradation of atracurium in plasma, its kinetics is theoretically independent of renal and liver functions.
Category:
Anaesthesia
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