Antidote for organophosphate insecticide poisoning: atropine and pralidoxime

Acute organophosphate (OP) poisoning produces cholinergic symptoms resulting from the inhibition of cholinesterase, and the overstimulation of muscarinic and nicotinic receptors in the synapses. The dominant clinical features of acute cholinergic toxicity include bradycardia, miosis, lacrimation, salivation, bronchorrhea, and bronchospasm. All symptomatic patients should receive therapy with oxygen, atropine, and pralidoxime. Atropine works as a physiologic antidote by competitively occupying muscarinic receptor sites, reducing the effects of excessive acetylcholine. Atropine should be immediately administered, and the dose can be titrated according to the severity of OP poisoning. A large dose may be necessary to overcome the excessive cholinergic state in case of severe poisoning. Pralidoxime is a biochemical antidote that reactivates acetylcholinesterase by removing OP from it. It is effective in treating both muscarinic and nicotinic symptoms. After some period of time, the acetylcholinesterase-OP compound undergoes a conformational change, known as aging, which renders the enzyme irreversibly resistant to reactivation by a pralidoxime. There has been a great deal of controversy over the effectiveness of pralidoxime in acute OP poisoning. However, it may be beneficial to administer pralidoxime for a sufficient period in case of severe poisoning with a large quantity of OP, which is common in Korea.