What is the treatment for chlorpyriphos (organophosphate) and cypermethrin poisoning?

Treatment of Chlorpyrifos and Cypermethrin Poisoning

Immediate treatment requires atropine for cholinergic symptoms, pralidoxime (2-PAM) for organophosphate poisoning within 36 hours of exposure, supportive care including airway management and decontamination, with cautious use of low-dose atropine when treating mixed organophosphate-pyrethroid poisoning to avoid atropine toxicity. 1, 2, 3

Immediate Management Algorithm

Decontamination and Supportive Care

• Remove all contaminated clothing and wash hair and skin thoroughly with sodium bicarbonate or alcohol as soon as possible 1
• Ensure airway management, respiratory and cardiovascular support, correction of metabolic abnormalities, and seizure control in severe cases 1
• Maintain observation for at least 48-72 hours due to risk of continuing absorption from the lower bowel and fatal relapses 1

Atropine Administration

• Atropine should be given only after hypoxemia is improved, never in the presence of significant hypoxia due to risk of ventricular fibrillation 1
• In adults, give 2-4 mg intravenously, repeated at 5-10 minute intervals until full atropinization (secretions are inhibited) or signs of atropine toxicity appear (delirium, hyperthermia, muscle twitching) 1
• For mixed organophosphate-pyrethroid poisoning, use LOW-DOSE atropine only as needed to avoid complications from excessive atropinization 3
• Maintain some degree of atropinization for at least 48 hours until depressed blood cholinesterase activity is reversed 1

Pralidoxime (2-PAM) Administration

• Administer pralidoxime after atropine effects become apparent, ideally within 36 hours of exposure for maximum effectiveness 1
• Generally, little is accomplished if pralidoxime is given more than 36 hours after termination of exposure 1
• Administer slowly, preferably by infusion; if IV not feasible, use intramuscular or subcutaneous injection 1
• "Titrate" the patient with pralidoxime as long as signs of poisoning recur, with additional doses every 3-8 hours if needed 1
• Therapeutic plasma concentration is minimum 4 µg/mL, reached in about 16 minutes after 600 mg injection 1
• Consider continuous IV infusion (400-600 mg/hr) to maintain therapeutic levels longer than intermittent dosing 1

Clinical Recognition of Poisoning Severity

Organophosphate (Chlorpyrifos) Toxicity Features

• Cholinergic syndrome: miosis (constricted pupils), excessive salivation, bronchospasm, bradycardia, urination, defecation, and muscle fasciculations 4
• Chlorpyrifos causes irreversible acetylcholinesterase inhibition leading to acetylcholine accumulation 5, 4
• Mild symptoms include blurred vision, teary eyes, runny nose, increased salivation, chest tightness, tremors, nausea 1
• Severe symptoms include confused behavior, severe respiratory difficulty, severe muscular twitching, involuntary urination/defecation, convulsions, unconsciousness 1

Pyrethroid (Cypermethrin) Toxicity Features

• Cypermethrin can present with an organophosphate-like toxidrome, creating diagnostic confusion 3
• Predominantly neurological and gastrointestinal symptoms, with seizures occurring in 15-19% of cases 6, 7
• Prolonged bradycardia may occur and respond to low-dose atropine 8
• Severe pyrethroid poisoning is rare but can mimic organophosphate poisoning 3

Mixed Chlorpyrifos-Cypermethrin Poisoning

• Mixed poisoning appears more toxic than either pesticide alone, with higher rates of respiratory failure (58.3% vs 48.8% for chlorpyrifos alone vs 11.1% for cypermethrin alone) 7
• Organophosphates inhibit carboxylesterases that detoxify pyrethroids, potentially increasing combined toxicity 6, 7
• Patients with mixed poisoning have significantly shorter ventilator-free days (20.9 ± 9.3 days vs 26.1 ± 4.4 days for chlorpyrifos alone) 6
• Lower Glasgow Coma Scale scores and serum cholinesterase levels compared to single-agent poisoning 7
• Mortality rates range from 13-17% in mixed poisoning cases 6, 7

Critical Pitfalls to Avoid

• Never give atropine in the presence of significant hypoxia - correct hypoxemia first to prevent atropine-induced ventricular fibrillation 1
• Avoid morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers in organophosphate poisoning 1
• Use succinylcholine with extreme caution due to risk of prolonged paralysis with anticholinesterase drugs 1
• Do not assume cypermethrin poisoning is benign - it can present with severe organophosphate-like symptoms requiring aggressive treatment 3, 7
• Monitor for continuing absorption from the GI tract, as fatal relapses have occurred after initial improvement 1

Monitoring and Disposition

• Keep patients under observation for at least 48-72 hours regardless of initial improvement 1
• Monitor for aspiration pneumonia (occurs in 44.6% of cases), acute respiratory failure (41.3%), acute kidney injury (13.9%), and seizures (7.5%) 7
• Expect leukocytosis and elevated C-reactive protein as common laboratory findings 7
• Ventilatory support required in 42-54% of chlorpyrifos cases and 16% of cypermethrin cases 6