L Cysteine

L CYSTEINE

L-cysteine is an endogenous amino acid that is often added to total parenteral nutrition regimens to enhance calcium and phosphate solubility. The ultrashort-acting neuromuscular blocker,gantacurium, and other fumarates rapidly combine with L-cysteine in vitro to form less active degrada-tion products (adducts). Exogenous administration of L-cysteine (10–50 mg/kg intravenously) given to anesthetized monkeys 1 min after these neuromus-cular blocking agents abolished the block within 2–3 min; this antagonism was found to be superior to that produced by anticholinesterases. This unique method of antagonism by adduct formation and inactivation is still in the investigative stage, especially in terms of its safety and efficacy in humans.