What is the treatment for propoxur (carbamate) poisoning?

Treatment of Propoxur (Carbamate) Poisoning

Immediately administer atropine as the life-saving first-line treatment, but do NOT give pralidoxime for confirmed propoxur poisoning—pralidoxime is contraindicated in carbamate toxicity and may worsen the poisoning. 1, 2

Critical Initial Actions

Decontamination and Personal Protection:

• Use appropriate personal protective equipment to prevent healthcare provider contamination 1
• Remove all contaminated clothing immediately and perform copious irrigation with soap and water for external exposure 1

Airway Management:

• Perform early endotracheal intubation for life-threatening poisoning, particularly when bronchorrhea, bronchospasm, or altered mental status threatens airway protection 1
• Avoid succinylcholine and mivacurium for intubation—these neuromuscular blockers are metabolized by cholinesterase and are absolutely contraindicated 1

Atropine Dosing Algorithm

Initial Dosing:

• Adults: 1-2 mg IV immediately for severe manifestations (bronchospasm, bronchorrhea, seizures, or significant bradycardia) 1
• Children: 0.02 mg/kg IV (minimum 0.1 mg, maximum single dose 0.5 mg) 1

Dose Escalation:

• Double the dose every 5 minutes until full atropinization is achieved 1
• Therapeutic endpoints include: clear chest on auscultation, heart rate >80/min, systolic blood pressure >80 mm Hg, dry skin and mucous membranes, and mydriasis 1
• Do not stop atropine due to tachycardia—tachycardia is an expected pharmacologic effect and not a contraindication to continued administration 3

Maintenance Therapy:

• Maintain atropinization with continuous infusion after initial bolus dosing 1

Pralidoxime: Critical Contraindication

The FDA drug label explicitly states that pralidoxime (PROTOPAM Chloride) is NOT indicated as an antidote for carbamate pesticide poisoning and may increase the toxicity of carbamates like propoxur. 2

However, there is one important clinical caveat:

• If the class of poison is unknown (organophosphate versus carbamate), pralidoxime should not be withheld, as organophosphate poisoning is clinically indistinguishable from carbamate poisoning and requires early oxime therapy 1
• Once propoxur is confirmed as the specific poison, pralidoxime should be discontinued 2

Seizure Management

• Administer benzodiazepines (diazepam first-line or midazolam) to treat seizures and agitation 1

Supportive Care Essentials

• Provide supplemental oxygen and support ventilation as needed 1
• Establish IV access and administer fluids for volume resuscitation 1
• Perform continuous cardiac monitoring for dysrhythmias 1
• Monitor closely for at least 48-72 hours as delayed complications can occur 1

Key Mechanistic Difference from Organophosphates

Carbamates like propoxur spontaneously dissociate from acetylcholinesterase, unlike organophosphates which form permanent covalent bonds ("aging") 4. This reversible binding is why pralidoxime is not only unnecessary but potentially harmful in carbamate poisoning 2.

Monitoring for Complications

• Watch for aspiration pneumonia from bronchorrhea 1
• Monitor for rhabdomyolysis and renal damage, though this is more common with organophosphates 1
• Assess for central nervous system effects including hallucinations and fever from high-dose atropine therapy 1

Expert Consultation

Contact poison control (1-800-222-1222 in the US) for expert guidance on specific case management 1