Pralidoxime
Pralidoxime chloride / 2-pyridine aldoxime methyl chloride
Also known as: Protopam · 2-PAM · Pralidoxime chloride · Pralidoxime mesilate · 2-pyridine aldoxime methyl chloride
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 toxicity | 10-20 mg/kg | IV/IM/SC | bid to tid | Until nicotinic signs resolve (usually 1-2 days) | 🌍 EU |
- Organophosphate toxicity: Administer IV very slowly over 15-30 minutes. Can also be given as a continuous rate infusion (CRI). Must be given in conjunction with atropine.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Organophosphate toxicity | 10-20 mg/kg | IV/IM/SC | bid to tid | Until nicotinic signs resolve (usually 1-2 days) | 🌍 EU |
- Organophosphate toxicity: Administer IV very slowly over 15-30 minutes. Must be given in conjunction with atropine.
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 in veterinary medicine to treat organophosphate (OP) toxicity. It is used to reverse the neuromuscular paralysis associated with OP poisoning.
Warning: Pralidoxime is generally contraindicated for carbamate toxicity as it may worsen the clinical picture or provide no benefit.
Clinical Pearl: Pralidoxime does not cross the blood-brain barrier well; therefore, it primarily relieves peripheral nicotinic signs (muscle tremors, weakness, paralysis) but not central nervous system signs. It must always be used in conjunction with atropine, which addresses the life-threatening muscarinic signs (bradycardia, bronchoconstriction, and SLUDGE: salivation, lacrimation, urination, defecation, GI upset, emesis). To be effective, pralidoxime must be administered early, before the OP-enzyme complex undergoes 'aging' (permanent irreversible binding), which typically occurs within 24-48 hours of exposure.
Mechanism of action
Pralidoxime works by reactivating the acetylcholinesterase (AChE) enzyme that has been inactivated by organophosphate binding. It binds to the OP-AChE complex → cleaves the phosphate bond → releases the OP → restores the enzyme's ability to break down acetylcholine at the synaptic cleft.
Additionally, it directly detoxifies certain unbound OP molecules through chemical inactivation and retards the 'aging' of phosphorylated cholinesterase into a non-reactive, permanently damaged form.
Safety & warnings
Contraindications
- Carbamate toxicity (can exacerbate toxicity)
- Poisoning by non-anticholinesterase compounds
- Hypersensitivity to pralidoxime
Adverse effects
- Tachycardia
- Muscle rigidity
- Transient neuromuscular blockade (if given too rapidly IV)
- Hypertension
- Hyperventilation
Precautions
Rapid IV Administration: Must be given slowly (over 15-30 minutes). Rapid intravenous injection can cause tachycardia, cardiac arrest, and paradoxical muscle rigidity or neuromuscular blockade.
- Timing is critical: Efficacy drops significantly if administered >24-48 hours post-exposure due to enzyme 'aging'.
- Renal Impairment: Use with caution and reduce dose in patients with renal failure, as the drug is primarily excreted unchanged in the urine.
- Concurrent Therapy: Always ensure adequate atropinization and airway management before or during pralidoxime administration.
Drug interactions
May exacerbate organophosphate toxicity
Prolonged neuromuscular blockade due to cholinesterase inhibition
May exacerbate respiratory depression in OP toxicity
May exacerbate toxicity
Monitoring
- Heart rate and rhythm (ECG)
- Respiratory rate and effort
- Resolution of muscle fasciculations and weakness
- Blood pressure
- Renal function (urine output)
Pharmacokinetics
Half-life
Absorption
Poorly absorbed orally; must be given parenterally. Peak plasma concentrations are reached rapidly after IM or SC injection.
Distribution
Distributed primarily in extracellular fluid. It is a quaternary ammonium compound and does not readily cross the blood-brain barrier.
Metabolism
Metabolized in the liver to a small extent.
Elimination
Rapidly excreted in the urine, primarily as unchanged drug via active tubular secretion.
Overdose
Overdose can cause paradoxical neuromuscular blockade, muscle rigidity, tachycardia, and worsening of cholinergic signs. Treatment is supportive, including artificial ventilation if respiratory paralysis occurs.
Available products
Formulations
- Powder for reconstitution: 1 g vial (produces 50 mg/ml solution)
Human-labeled
- Protopam Chloride 1 g powder for injection
Regulatory status
Human approved drug used extra-label in veterinary medicine.
Available as a POM (Prescription Only Medicine).
POM-V or POM depending on specific formulation.
No regulatory data for: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store intact vials at room temperature. Reconstituted solutions should be used promptly as they generally do not contain preservatives. Discard any unused portion.
Client information
Pralidoxime is an emergency antidote used exclusively in a veterinary hospital setting to treat severe poisoning from certain insecticides or pesticides (organophosphates).
- It works by 'un-sticking' the poison from a vital enzyme in your pet's body, helping to restore normal muscle function and breathing.
- It is almost always given alongside another antidote called atropine.
- Time is of the essence; this medication is most effective when given within the first 24 hours of exposure.
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.