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Key Features

  • Includes organophosphates and carbamates

  • Inhibit the enzyme acetylcholinesterase and increase acetylcholine activity at nicotinic and muscarinic receptors and in CNS

  • Most are absorbed through intact skin

  • Most chemical warfare "nerve agents" (such as GA [tabun], GB [sarin], GD [soman] and VX) are organophosphates

Clinical Findings

  • Abdominal cramps

  • Diarrhea

  • Vomiting

  • Excessive salivation

  • Sweating

  • Seizures

  • Lacrimation

  • Constricted pupils

  • Wheezing

  • Bronchorrhea

  • Skeletal muscle fasciculations

  • Weakness

  • Respiratory arrest

  • Initial tachycardia may be followed by bradycardia

  • Symptoms may persist or recur for days, especially with highly lipid-soluble agents such as fenthion or dimethoate

Diagnosis

  • Serum and red blood cell cholinesterase activity is usually at least 50% below baseline with severe intoxication

  • Serum or urine levels of specific pesticides rarely available nor helpful

Treatment

  • For recent ingestions, consider gut decontamination by aspiration of the liquid using a nasogastric tube followed by administration of activated charcoal

  • If the agent is on the victim's skin or hair, wash with soap or shampoo and water

  • Care providers should avoid skin exposure by wearing gloves and waterproof aprons

  • Dilute hypochlorite solution (eg, household bleach diluted 1:10) is reported to help break down organophosphate pesticides and nerve agents on equipment or clothing

  • Administer atropine, 2 mg intravenously, and give repeated doses as needed (may need several hundred milligrams) to dry bronchial secretions and decrease wheezing

  • Administer pralidoxime, 1–2 g intravenously, as soon as possible, and give a continuous infusion (200–500 mg/h) as long as there is any evidence of acetylcholine excess

  • Pralidoxime is of questionable benefit for carbamate poisoning

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