Pralidoxime is an antidote to organophosphate pesticides and chemicals. Organophosphates bind to the esteratic site of acetylcholinesterase, which results initially in reversible inactivation of the enzyme. If given within 24 hours,after organophosphate exposure, pralidoxime reactivates the enzyme cholinesterase by cleaving the phosphate-ester bond formed between the organophosphate and acetylcholinesterase.
Indication
For the treatment of poisoning due to those pesticides and chemicals of the organophosphate class which have anticholinesterase activity and in the control of overdosage by anticholinesterase drugs used in the treatment of myasthenia gravis.
Pharmacology
Pralidoxime is to reactivate cholinesterase (mainly outside of the central nervous system) which has been inactivated by phosphorylation due to an organophosphate pesticide or related compound. The destruction of accumulated acetylcholine can then proceed, and neuromuscular junctions will again function normally. Pralidoxime also slows the process of "aging" of phosphorylated cholinesterase to a nonreactivatable form, and detoxifies certain organophosphates by direct chemical reaction. The drug has its most critical effect in relieving paralysis of the muscles of respiration. Because pralidoxime is less effective in relieving depression of the respiratory center, atropine is always required concomitantly to block the effect of accumulated acetylcholine at this site. Pralidoxime relieves muscarinic signs and symptoms, salivation, bronchospasm, etc., but this action is relatively unimportant since atropine is adequate for this purpose.
Affected Organisms
Humans and other mammals
Biotransformation
Hepatic
Half Life
74-77 minutes
Protein Binding
No binding to plasma proteins
Elimination
The drug is rapidly excreted in the urine partly unchanged, and partly as a metabolite produced by the liver.
Biochem/physiol Actions The prototypical reactivator of acetylcholinesterase that has been inactivated by organophosphorus insecticides or nerve agents. It is now known that no reactivator is effective against a broad spectrum of organophosphorus agents.1
Biochem/physiol Actions The prototypical reactivator of acetylcholinesterase that has been inactivated by organophosphorus insecticides or nerve agents. It is now known that no reactivator is effective against a broad spectrum of organophosphorus agents.1
Harmful (Xn)
Irritant (Xi)