Pralidoxime Chloride
2-Formyl-1-methylpyridinium chloride oxime
Also known as: Protopam Chloride · 2-Formyl-1-methylpyridinium chloride oxime · 2-PAM chloride · 2-PAMCl · 2-pyridine aldoxime methochloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate poisoning | 20 mg/kg | IM or slow IV | 2-3 times a day | — | 🌎 NA |
| Organophosphate poisoning | 10-15 mg/kg | IM or SC | q8-12h | 36 hour minimum | 🌎 NA |
| Organophosphate poisoning | 50 mg/kg | slow IV | May repeat in one hour if severe | Recovery should occur gradually over 48 hours | 🌎 NA |
| Organophosphate poisoning | 50 mg/kg | IV | Repeat in one hour if signs persist, then q8h | 24-48 hours | 🌎 NA |
- Organophosphate poisoning: Works best when combined with atropine. Initial dose IM or slow IV; subsequent doses IM or SC.
- Organophosphate poisoning: Give atropine first (0.1 mg/kg IV, then 0.3 mg/kg IM). Dilute pralidoxime in 10% glucose. For small dogs, may administer IM or IP. Reduce dose in renal failure.
- Organophosphate poisoning: Give slowly or with fluids over a 30-minute period. If clinical signs intensify (e.g., respiratory depression), reduce dose and give as repeated one-hour infusions every 4-8 hours in combination with atropine.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate poisoning | 20 mg/kg | IM or slow IV | 2-3 times a day | — | 🌎 NA |
| Organophosphate poisoning | 10-15 mg/kg | IM or SC | q8-12h | 36 hour minimum | 🌎 NA |
| Organophosphate poisoning | 50 mg/kg | slow IV | May repeat in one hour if severe | Recovery should occur gradually over 48 hours | 🌎 NA |
| Organophosphate poisoning | 20 mg/kg | IV | Repeat in one hour if signs persist, then q8h | 24-48 hours | 🌎 NA |
| Organophosphate poisoning | 20 mg/kg | IM or IV | May repeat q6-8h | — | 🌎 NA |
- Organophosphate poisoning: Works best when combined with atropine. Initial dose IM or slow IV; subsequent doses IM or SC.
- Organophosphate poisoning: Give atropine first. Dilute in 10% glucose. May administer IM or IP. Reduce dose in renal failure.
- Organophosphate poisoning: Give slowly or with fluids over a 30-minute period.
- Organophosphate poisoning: Give within first 24 hours of exposure. Combine with atropine or give separately. Do not use in carbamate toxicity.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate poisoning | 10-20 mg/kg | Not specified | q8-12h | — | 🌎 NA |
| Organophosphate poisoning | 10-100 mg/kg | IM | q24-48h or repeat once in 6 hours | — | 🌎 NA |
- Organophosphate poisoning: Give with atropine (0.2-0.5 mg/kg IM q3-4h).
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate poisoning | 20 mg/kg (may require up to 35 mg/kg) | IV | q4-6h | — | 🌎 NA |
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate poisoning | 30 mg/kg | IM | q8h | — | 🌎 NA |
| Organophosphate poisoning | 25-50 mg/kg | IV | Single dose, or maximum of 100 mg/kg/day as an IV drip | — | 🌎 NA |
- Organophosphate poisoning: FARAD recommends a 28-day meat and a 6-day milk withdrawal time.
- Organophosphate poisoning: Give as a 20% solution over 6 minutes.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Pralidoxime (often referred to as 2-PAM) is a specific antidote used primarily in veterinary medicine to treat organophosphate (OP) toxicity. Organophosphates are commonly found in older insecticides, agricultural chemicals, and some nerve agents. They work by irreversibly binding to and inhibiting acetylcholinesterase (AChE), leading to a massive accumulation of acetylcholine at nerve synapses and neuromuscular junctions.
Pralidoxime acts as a cholinesterase reactivator, effectively pulling the OP molecule off the enzyme before the bond becomes permanent (a process known as "aging").
Clinical Pearl: Pralidoxime is almost always used in conjunction with atropine. While atropine blocks the muscarinic effects of acetylcholine excess (SLUDDE signs: salivation, lacrimation, urination, defecation, dyspnea, emesis), pralidoxime is required to alleviate the nicotinic effects, particularly profound muscle tremors, weakness, and paralysis (including respiratory muscles). It is generally not recommended for carbamate toxicity, as carbamate-AChE bonds spontaneously reverse without the need for an oxime reactivator.
Mechanism of action
Pralidoxime works by directly reactivating the acetylcholinesterase enzyme that has been inhibited by organophosphates.
- Organophosphates bind to the esteratic site of acetylcholinesterase (AChE) via phosphorylation, inactivating the enzyme.
- Accumulation of acetylcholine (ACh) occurs at muscarinic and nicotinic receptors → severe overstimulation.
- Pralidoxime possesses a high affinity for the AChE enzyme.
- Via nucleophilic attack, the oxime group of pralidoxime binds to the offending phosphoryl group of the organophosphate.
- The pralidoxime-organophosphate complex breaks away from the enzyme → AChE is reactivated and resumes breaking down ACh.
Important Mechanistic Note: If the phosphorylated enzyme undergoes a chemical change (loss of an alkyl group) before pralidoxime is administered, the bond becomes permanent. This is known as "aging". Therefore, pralidoxime is most effective when given within 24 hours of exposure, though some benefit may be seen up to 36-48 hours in massive exposures.
Safety & warnings
Contraindications
- Hypersensitivity to pralidoxime
- Carbamate poisoning (generally not recommended as inhibition is rapidly reversible)
Adverse effects
- Tachycardia (especially with rapid IV injection)
- Muscle rigidity
- Transient neuromuscular blockade
- Laryngospasm
Precautions
Use with caution in patients receiving anticholinesterase agents for the treatment of myasthenia gravis, as it may precipitate a myasthenic crisis. Use cautiously and at a reduced dosage rate in patients with renal impairment. Must generally be given within 24 hours of exposure to be effective. Rapid IV injection should be avoided to prevent tachycardia, muscle rigidity, and laryngospasm.
Drug interactions
Anticholinesterases can potentiate the action of barbiturates; use with caution.
Use should be avoided in patients with organophosphate toxicity.
Use should be avoided in patients with organophosphate toxicity.
Use should be avoided in patients with organophosphate toxicity.
Use should be avoided in patients with organophosphate toxicity.
Use should be avoided in patients with organophosphate toxicity.
Monitoring
- Clinical signs associated with organophosphate poisoning (SLUDDE signs, muscle fasciculations, weakness)
- Heart rate and rhythm (especially during IV administration)
- Respiratory rate and effort
Pharmacokinetics
Absorption
Marginally absorbed after oral dosing; oral dosage forms are no longer available in the United States.
Distribution
Distributed primarily throughout the extracellular water. Because of its quaternary ammonium structure, it is historically not believed to enter the CNS in significant quantities, but recent studies and clinical responses have led some to question this belief.
Metabolism
Thought to be metabolized by the liver.
Elimination
Excreted as both metabolite(s) and unchanged drug in the urine.
Overdose
The acute LD50 of pralidoxime in dogs is 190 mg/kg. At high dosages, it causes signs associated with its own anticholinesterase activity.
Clinical signs of toxicity in dogs may be exhibited as:
- Muscle weakness
- Ataxia
- Vomiting
- Hyperventilation
- Seizures
- Respiratory arrest
- Death
Available products
Formulations
- Powder for injection
Human-labeled
- Pralidoxime Chloride Powder for Injection: 1 gram in 20 mL single-use vials (Protopam Chloride)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Unless otherwise instructed by the manufacturer, pralidoxime chloride powder for injection should be stored at room temperature. After reconstituting with sterile water for injection, the solution should be used within a few hours. Do not use sterile water with preservatives added.
Client information
- Emergency Treatment: This medication is a critical, life-saving antidote for specific types of pesticide or nerve agent poisonings (organophosphates).
- Hospitalization Required: Your pet will need to be hospitalized and closely monitored by veterinary professionals while receiving this drug.
- Time-Sensitive: This antidote is most effective when given as soon as possible after exposure (ideally within the first 24 hours).
- Combination Therapy: It is almost always given alongside another antidote called atropine to fully control the severe symptoms of poisoning.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.