Pralidoxime

Pralidoxime, also called 2-PAM, is an oxime antidote used mainly in organophosphate poisoning. Its clinical purpose is restoration of inhibited acetylcholinesterase, complementing atropine and supportive treatment. Veterinary applications include insecticide or other organophosphate exposures, with response influenced by the compound involved and the chemical state of the inhibited enzyme.

Group

Oxime antidote

Mechanism of Action

Pralidoxime binds near the organophosphate-inhibited acetylcholinesterase active site and removes the phosphoryl group, reactivating the enzyme before the inhibited complex has aged. Restored acetylcholine breakdown reduces excessive stimulation at peripheral cholinergic synapses, including neuromuscular junctions. Limited central nervous system penetration means the principal reactivation effect is peripheral.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–50 mg/kg	IM, IV	Every 8–12 h	Slow initial IV administration; individualize to recurrence of clinical signs.
Organophosphate poisoning — Initial	20 mg/kg	IM, IV	Once	Slow IV; subsequent doses may use IM or SC.
Organophosphate poisoning — Maintenance	20 mg/kg	IM, SC	Every 8–12 h
Organophosphate poisoning	10–15 mg/kg	IM, SC	Every 8–12 h	Alternative at least 36-hour course.
Organophosphate poisoning	50 mg/kg	IV	Every 8 h	Give over 30 minutes; may repeat once after 1 hour if signs persist, then every 8 hours for 24-48 hours.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–50 mg/kg	IM, IV	Every 8–12 h	Slow initial IV administration; individualize to recurrence of clinical signs.
Organophosphate poisoning — Initial	20 mg/kg	IM, IV	Once	Slow IV; subsequent doses may use IM or SC.
Organophosphate poisoning — Maintenance	20 mg/kg	IM, SC	Every 8–12 h
Organophosphate poisoning	10–15 mg/kg	IM, SC	Every 8–12 h	Alternative at least 36-hour course.
Organophosphate poisoning	20 mg/kg	IM, IV	Every 6–8 h	Early treatment within 24 hours; slow IV.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–50 mg/kg	IM, IV	Every 8 h	Reported large-animal regimen uses a 10% solution; slow IV infusion or repeat based on signs.
Organophosphate poisoning	30 mg/kg	IM	Every 8 h
Organophosphate poisoning	25–50 mg/kg	IV		20% solution infused over 6 minutes.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–50 mg/kg	IM, IV	Every 8 h	Reported large-animal regimen uses a 10% solution; slow IV infusion or repeat based on signs.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–50 mg/kg	IM, IV	Every 8 h	Reported large-animal regimen uses a 10% solution; slow IV infusion or repeat based on signs.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	20–35 mg/kg	IV	Every 4–6 h

Birds

Use / stage	Dose	Route	Schedule	Instructions
Organophosphate poisoning	10–100 mg/kg	IM	Every 24–48 h	Separate report allows one repeat after 6 hours.

Indications

Adjunctive treatment of organophosphate poisoning in veterinary patients, particularly to restore peripheral acetylcholinesterase activity and neuromuscular function.

Contraindications

Carbamate intoxication: reported advises against treatment.
Avoid rapid IV administration.

Interactions

Avoid aminoglycosides, barbiturates, phenothiazines and neuromuscular blockers during organophosphate poisoning when possible.

Adverse effects

Pain with IM injection; rapid IV use can cause muscle spasm and cardiorespiratory problems.

Toxicity

High exposure can itself cause cholinergic-type weakness, ataxia, vomiting, hyperventilation, seizures or respiratory arrest.

Preparations

Preparation	Form	Strength	Route
Pralidoxime chloride 1 g vial	Injection	1000 mg / vial	IV, IM
Pralidoxime chloride reconstituted 50 mg/mL Reported confirms 1 g reconstituted to 20 mL; discard after 3 hours.	Injection	50 mg / mL	IV, IM

Monitoring and Administration

Treat promptly with atropine as part of the antidotal plan; reported regimen describes atropine 0.1 mg/kg without a specified route here. Monitor rhythm, ventilation, recurrent cholinergic signs and available cholinesterase testing.

Dilute in glucose solution for slow IV infusion. Protect reconstituted solution from light below 25 C and discard after 3 hours.

One severe-poisoning protocol gives atropine 0.1 mg/kg IV then 0.3 mg/kg IM before pralidoxime 50 mg/kg in 10% glucose slowly IV; repeat at 1 hour if weakness persists. Renal failure requires reduction. A ruminant infusion maximum 100 mg/kg/day and bird route-unspecified 10-20 mg/kg every 8-12 hours are not generic bolus regimens.