Acetylcholinesterase reactivation in the brain of parathion poisoned dogs

In vivo-reactivation of alkylphosphorylated cholinesterases has been studied in blood and various brain areas of dogs poisoned with parathion and treated with 10 or 20 mg/kg of obidoxime. Whereas acetylcholinesterase of erythrocytes was almost completely reactivated plasmacholinesterase was mostly unaffected. Acetylcholinesterase was more readily reactivated in brain cortex and thalamus than in medulla oblongata, cerebellum and nucleus caudatus. No reactivation could be measured in the nucleus lentiformis. Data from brain of a poisoned patient who was treated but died due to other causes suggest that reactivation may also occur in humans. Optimal treatment of alkylphosphate intoxication may require a loading dose of 10 mg/kg obidoxime i.v. prior to an i.v. infusion of 5 mg/kg per hour for 12 hours.