What is the treatment for insecticide poisoning?

Treatment of Insecticide Poisoning

For organophosphate insecticide poisoning, immediate administration of atropine is the cornerstone of treatment, with pralidoxime as an adjunctive therapy, though its clinical benefit remains controversial. 1, 2

Immediate Management

Atropine Administration

• Atropine should be given as soon as possible after hypoxemia is improved to prevent atropine-induced ventricular fibrillation in the presence of significant hypoxia 1
• Initial adult dose: 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
• Maintain some degree of atropinization for at least 48 hours until depressed blood cholinesterase activity is reversed 1
• In children, doses as high as 0.1 mg/kg may be needed, which is substantially higher than typical pediatric resuscitation doses 3
• Do not stop atropine in the presence of tachycardia in children, as repeated boluses do not cause cardiac arrhythmias in this population, unlike adults 3
• Large doses up to 5 grams may be required in severe cases 4

Pralidoxime (Oxime Therapy)

• Initial dose: 1000-2000 mg intravenously as an infusion in 100 mL normal saline over 15-30 minutes 1
• The FDA-approved regimen should be administered slowly, preferably by infusion 1
• Pralidoxime is most effective if initiated immediately after poisoning and generally accomplishes little if given more than 36 hours after exposure 1

Important caveat: Despite FDA approval and widespread use, the largest randomized controlled trial found no survival benefit from pralidoxime, even though it successfully reactivated red cell acetylcholinesterase 2. The mortality was actually nonsignificantly higher in the pralidoxime group (24.8% vs 15.8%, HR 1.69) 2. However, this remains the standard of care per FDA labeling 1.

Supportive Care Priority

• Establish airway management and correct hypoxemia BEFORE administering atropine 1
• Provide respiratory and cardiovascular support as needed 1
• Correct metabolic abnormalities and control seizures 1
• Maintain observation for at least 48-72 hours due to risk of relapse from continued absorption 1

Decontamination

• Remove all contaminated clothing immediately 1
• Wash hair and skin thoroughly with sodium bicarbonate or alcohol as soon as possible 1
• Perform gastric lavage if ingestion occurred 5
• Administer activated charcoal via nasogastric tube 5

Specific Contraindications and Warnings

What NOT to Use

• Pralidoxime is NOT effective for phosphorus, inorganic phosphates, or organophosphates without anticholinesterase activity 1
• Pralidoxime is contraindicated for carbamate insecticide poisoning as it may increase toxicity of carbaryl 1
• Avoid morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers 1
• Use succinylcholine with extreme caution due to prolonged paralysis risk 1

Alternative for Atropine Allergy

• If proven atropine allergy exists (rare but documented), use glycopyrrolate combined with benzodiazepines or scopolamine 6
• Glycopyrrolate provides peripheral antimuscarinic effects without central action 6

Pediatric Considerations

• Children are more susceptible to organophosphate toxicity due to higher minute ventilation and breathing closer to ground level where vapor concentrations are highest 3
• Convulsions occur more frequently in children due to rapid development of hypoxia from respiratory muscle weakness 3
• Administer obidoxime or pralidoxime chloride slowly to minimize side effects (nausea, hypotension with obidoxime; hypertension, headache with pralidoxime) 3
• For seizures: diazepam 0.2 mg/kg or midazolam 0.1 mg/kg repeatedly until complete cessation 3

Monitoring for Complications

Respiratory Failure

• Respiratory failure is the most common complication (74.4% of patients in one series) and the major cause of mortality 5
• Early recognition and intubation is life-saving - watch for increasing respiratory rate (e.g., 22 to 38 breaths/min indicates respiratory distress) 5
• Mechanical ventilation required in approximately 21% of cases, with 50% mortality in this subgroup 5

Intermediate Syndrome

• Occurs in approximately 19% of patients 5
• Characterized by respiratory muscle weakness developing 24-96 hours after initial cholinergic crisis
• Delayed intubation in intermediate syndrome is associated with mortality 5

Continuing Absorption

• When poison is ingested, continuing absorption from the lower bowel constitutes new exposure 1
• Fatal relapses have been reported after initial improvement 1
• Additional pralidoxime doses may be needed every 3-8 hours - essentially "titrate" the patient as long as signs of poisoning recur 1

Common Pitfalls

• Failing to maintain adequate atropinization for 48+ hours is a frequent cause of treatment failure 4
• Administering atropine before correcting hypoxemia risks ventricular fibrillation 1
• Assuming improvement means treatment can stop - absorption may continue for days 1
• Using pralidoxime for carbamate poisoning, which can worsen toxicity 1