pralidoxime

Pralidoxime is a cholinesterase reactivator used as the antidote to organophosphate pesticides or acetylcholinesterase inhibitors (nerve agents) in conjunction with atropine and diazepam. Organophosphates bind to the esteratic site of acetylcholinesterase, which results initially in reversible inactivation of the enzyme. Acetylcholinesterase inhibition causes acetylcholine to accumulate in synapses, producing continuous stimulation of cholinergic fibers throughout the nervous systems. If given within 24 hours after organophosphate exposure, pralidoxime reactivates the acetylcholinesterase by cleaving the phosphate-ester bond formed between the organophosphate and acetylcholinesterase. Pralidoxime is indicated as an adjunct in the treatment of moderate and severe poisoning caused by organophosphate pesticides that have anticholinesterase activity or by chemicals with anticholinesterase activity such as some chemicals used as nerve agents during chemical warfare. Pralidoxime is also indicated as an adjunct in the management of the overdose of cholinesterase inhibitors, such as ambenonium, neostigmine, and pyridostigmine, used in the treatment of myasthenia gravis. Pralidoxime, used in conjunction with atropine, reverses nicotinic effects, such as muscle weakness and fasciculation, respiratory depression, and central nervous system (CNS) effects, associated with toxic exposure to organophosphate anticholinesterase pesticides and chemicals and with cholinesterase inhibitor overdose. Atropine, by antagonizing the action of cholinesterase inhibitors at muscarinic receptor sites, reverses muscarinic effects, such as tracheobronchial and salivary secretion, bronchoconstriction, bradycardia, and, to a moderate extent, CNS effects. — NCATS