Pralidoxime (2-PAM): veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

2-PAM, Pralidoxime chloride, Protopam, Pralidoxime iodide

Species with doses

Dogs, Cats, Cattle, Horses, Sheep, Pigs and Birds

General dose range

20–50 mg/kg IM q8–12h (early in poisoning) — check the species tables for the indication

Routes

IM, IV

Last reviewed

1 October 2026

Indications

• Organophosphate insecticide poisoning (the specific reactivator) — with atropine
• Reversal of nicotinic signs (muscle fasciculation, weakness, respiratory-muscle paralysis) of OP toxicosis

Pralidoxime (2-PAM) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Organophosphate poisoning (with atropine): Papich 5e: 20 mg/kg up to 50 mg/kg q8–12h IM or IV (first dose slowly, diluted in glucose). Plumb’s p.992: 20 mg/kg 2–3 times daily (Fikes 1990); 50 mg/kg slowly IV in 10% glucose after atropine, repeat in 1 h if weakness persists, then q8h for 24–48 h (El Bahri; Mount 1989). Works best early and with atropine; not for carbamates. Reduce in renal failure.

Cats

• Organophosphate poisoning: Plumb’s p.992: cats 20 mg/kg IM or IV within the first 24 h, repeat q6–8h, with atropine (Reid & Oehme 1989; Mount 1989). Papich 5e: 20–50 mg/kg q8–12h IM or IV. Not for carbamate toxicity.

Cattle

• Organophosphate poisoning: Plumb’s p.992: cattle 30 mg/kg IM q8h (Osweiler 2007); 25–50 mg/kg of a 20% solution IV over 6 min, or up to 100 mg/kg/day as an IV drip (Smith 1986). Papich 5e: 20–50 mg/kg q8h IM or slow IV. FARAD-recommended withdrawal for ruminants: 28 days meat, 6 days milk. Give with atropine.

Horses

• Organophosphate poisoning: Plumb’s p.992 (Oehme 1987): 20 mg/kg (up to 35 mg/kg) IV, repeated q4–6h. Give with atropine and supportive care.

Goats

• No reference dose for this species: Papich 5e gives cattle, sheep and pig doses, and Plumb’s 10e p.1052 gives only a cattle dose (30 mg/kg IM q8h, under its ruminants heading); neither gives a goat-specific dose. If used, FARAD recommends 28 days meat / 6 days milk withdrawal in ruminants.

Sheep

• Organophosphate poisoning (with atropine): Papich 5e: cattle, sheep and pigs 20–50 mg/kg q8h as a 10% solution IM or by slow IV infusion, as needed. FARAD ruminant withdrawal (Plumb’s): 28 days meat, 6 days milk. Give with atropine; early use only; not for carbamates.

Pigs

• Organophosphate poisoning (with atropine): Papich 5e: cattle, sheep and pigs 20–50 mg/kg q8h (10% solution) IM or slow IV. Obtain a FARAD withdrawal.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Organophosphate poisoning: Plumb’s p.992: cattle 30 mg/kg IM q8h (Osweiler 2007); 25–50 mg/kg of a 20% solution IV over 6 min, or up to 100 mg/kg/day as an IV drip (Smith 1986). Papich 5e: 20–50 mg/kg q8h IM or slow IV. FARAD-recommended withdrawal for ruminants: 28 days meat, 6 days milk. Give with atropine.

Birds

• Organophosphate poisoning: Carpenter's 6th ed (Bird toxicology table): 100 mg/kg IM once (goslings, diazinon toxicosis; lower doses 25–50 mg/kg less effective). Reactivates acetylcholinesterase — give WITH atropine. NOT for carbamate poisoning (worsens it). Plumb’s p.992: 10–20 mg/kg q8–12h with atropine 0.2–0.5 mg/kg IM q3–4h (Jones 2007); 10–100 mg/kg IM q24–48h or repeated once at 6 h (Johnson-Delaney & Reavill 2009).

Contraindications

Carbamate (reversible anticholinesterase) poisoning — generally not indicated and possibly detrimental; use atropine alone. Renal impairment (renally excreted — reduce dose). Rapid IV bolus (can cause weakness, tachycardia, laryngospasm — infuse slowly). Known hypersensitivity. Never use as a substitute for atropine.

Species-specific warnings

Cattle: Common with dip/spray organophosphate exposure — combine 2-PAM + atropine + washing off residual chemical; observe sensible food-animal withdrawal.

Adverse effects

• With rapid IV: transient weakness, tachycardia, hypertension, laryngospasm, muscle rigidity
• Injection-site pain (IM)
• Dizziness/incoordination
• Generally well tolerated when given correctly and early

Drug interactions

• Atropine: complementary and essential partner (atropine for muscarinic signs; 2-PAM for nicotinic/enzyme) — use together
• Other anticholinesterases / nicotine-like agents: additive effects
• Avoid morphine, succinylcholine, theophylline, reserpine and phenothiazines in OP-poisoned patients (can worsen)

Pregnancy and lactation

In a life-threatening OP poisoning the antidote should be given regardless; specific reproductive data are limited but maternal survival is the priority.

Monitoring

• Resolution of nicotinic signs (fasciculations, weakness, respiratory effort) and muscarinic signs (with atropine)
• Respiratory function (OP poisoning kills by respiratory failure)
• Heart rate/blood pressure during/after dosing
• Cholinesterase activity (blood) where available; renal function for dosing

Toxicity and overdose

Wide margin when given correctly. Rapid IV administration is the usual cause of adverse effects — transient weakness, tachycardia, hypertension, and laryngospasm/muscle rigidity. Excess in the absence of OP poisoning can itself mildly inhibit cholinesterase. Accumulates in renal failure.

Management: Slow or stop administration; supportive care for the transient neuromuscular/cardiovascular effects, which are short-lived. Provide ventilatory support if respiratory weakness. No specific antagonist; reduce dose in renal impairment.

Clinical pearls

• Two-drug antidote: ATROPINE handles the muscarinic crisis (salivation, bronchorrhoea, bradycardia), 2-PAM reactivates the enzyme and reverses the muscle/nicotinic signs — give both
• Time is enzyme: start 2-PAM as early as possible, before "aging" makes the OP–cholinesterase bond permanent
• Do NOT rely on 2-PAM for carbamate poisoning — atropine alone is the mainstay there
• A frontline antidote in India given the prevalence of organophosphate pesticide exposure in livestock and pets — keep it stocked
• Infuse slowly (dilute for IV) to avoid transient weakness/laryngospasm, and decontaminate the animal (wash off dermal OP) alongside antidotal therapy

Mechanism of action

Organophosphates inactivate acetylcholinesterase by phosphorylating its active site, so acetylcholine accumulates (muscarinic + nicotinic crisis). Pralidoxime has a high affinity for that phosphorus atom: it binds the OP and cleaves it from the enzyme, regenerating active acetylcholinesterase — particularly at the neuromuscular junction (nicotinic signs). This only works before "aging" (loss of an alkyl group) makes the OP–enzyme bond irreversible, hence the urgency.

Formulations and products

• Injection 50 mg/mL (5 %)
• Vial 1 g (reconstitute)
• Pralidoxime (PAM) — 500 mg / 1 g vial; 25–50 mg/mL, Injection (reconstitute) (human-label)

Storage

Injection/vials: 15–30 °C, protect from light. Reconstitute per label and use promptly.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other hormones, emergency drugs, supplements and other drugs

• Phenylpropanolamine (PPA)
• Phytonadione (Vitamin K1)
• PMSG / eCG (Pregnant Mare Serum Gonadotrophin)
• Potassium Bromide (KBr)
• Prazosin
• Prednisone
• Propentofylline
• Protamine Sulfate

Frequently asked questions