Why Is Paracetamol Toxic to Dogs?

Dogs have limited hepatic glucuronidation capacity compared to humans. Acetaminophen is predominantly metabolised via glucuronidation and sulfation in safe species, but in dogs, saturation of these pathways leads to accumulation of the toxic intermediate N-acetyl-p-benzoquinone imine (NAPQI). NAPQI binds to hepatocyte proteins causing centrilobular necrosis, and oxidises haemoglobin iron from Fe²⁺ to Fe³⁺, producing methemoglobin (MetHgb) that cannot carry oxygen.

Toxic Dose Thresholds

• Dogs: Clinical signs from ~100 mg/kg; severe toxicity ≥200 mg/kg
• Cats: Toxic from as little as 10 mg/kg — NEVER give to cats
• Hepatic necrosis: Primary concern in dogs at high doses
• Methemoglobinemia: Causes cyanosis, muddy/brown mucous membranes, dyspnoea
• Time to signs: GI signs within 1–4 hours; hepatotoxicity 24–72 hours

How to Use This Toxicity Calculator

1. Enter your dog’s body weight
2. Enter the total amount of paracetamol ingested (check the product label for mg per tablet)
3. Note the time since ingestion
4. Click Calculate — the tool will assess exposure severity
5. Call your vet or animal poison control immediately regardless of result

Treatment Overview (Veterinary)

• Decontamination: Induced emesis if <1 hour post-ingestion; activated charcoal
• N-acetylcysteine (NAC): 140 mg/kg loading IV, then 70 mg/kg q6h × 7 doses — replenishes glutathione
• Ascorbic acid: Reduces methemoglobin back to functional haemoglobin
• S-adenosylmethionine (SAMe): Hepatoprotective adjunct
• IV fluids, liver monitoring (ALT, bilirubin), methemoglobin measurement

References

1. Poppenga RH, Gwaltney-Brant SM. Small Animal Toxicology Essentials. Wiley-Blackwell; 2011.
2. Richardson JA. Management of acetaminophen and ibuprofen toxicoses in dogs and cats. J Vet Emerg Crit Care. 2000;10(4):285-291.
3. Osweiler GD. Toxicology. Williams & Wilkins; 1996.
4. ASPCA Animal Poison Control Center. Acetaminophen toxicity. 2023.