How quickly do NSAID toxicity signs appear in dogs and cats?

GI signs (vomiting, diarrhea, melena) typically appear within 2–24 hours. Renal signs may develop within 24–72 hours, especially with dehydration or pre-existing renal disease. CNS signs from ibuprofen in cats can appear within 4–6 hours.

Which NSAIDs are most dangerous to cats?

Ibuprofen and naproxen are extremely toxic to cats due to poor glucuronidation. Even small doses (5 mg/kg ibuprofen, 2 mg/kg naproxen) can cause severe GI ulceration, renal failure, and CNS signs. Aspirin has a narrow therapeutic index in cats.

What concurrent medications increase NSAID toxicity risk?

Concurrent corticosteroids, ACE inhibitors, and diuretics significantly increase the risk of GI ulceration and renal injury. Dehydration and hypovolemia also markedly increase renal toxicity risk.

Clinical decision support

NSAID toxicity calculator

Estimate NSAID overdose risk in dogs and cats with concurrent medication and hydration risk factors.

Reference ranges & assumptions

Default toxic thresholds (mg/kg) — Dog

Carprofen Meloxicam

Deracoxib Firocoxib

Aspirin Ibuprofen

Naproxen

Default toxic thresholds (mg/kg) — Cat

Carprofen Meloxicam

Aspirin Ibuprofen

Naproxen

Defaults are commonly cited GI/renal toxicity thresholds. Adjust to match your toxicology reference or institutional protocol.

NSAID dose

— mg/kg

Enter values

Enter weight and dose to calculate.

Risk level —

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GI ulceration risk —

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Renal risk —

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CNS risk —

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Clinical next steps

Induce emesis if within 2 hours and patient is asymptomatic. Consider activated charcoal for recent ingestions.
Initiate gastroprotectants: proton pump inhibitor (omeprazole 0.5–1 mg/kg PO/IV q12–24h) ± sucralfate.
For renal risk: start IV fluid therapy (lactated Ringer\'s or Normosol-R) at 2× maintenance for 24–48h.
Monitor BUN, creatinine, electrolytes, PCV/TS, and urinalysis at baseline, 24h, and 48h.
For ibuprofen in cats: monitor for CNS signs (ataxia, tremors, seizures); supportive care with IV fluids and diazepam if needed.
Check for concurrent steroid or ACE inhibitor use which increases GI and renal risk respectively.

Safety checks

This tool supports calculation and education only.
It does not diagnose, prescribe, or replace current clinical references.
Verify patient-specific decisions with current toxicology references, hospital protocols, and veterinarian judgment.
Cats are significantly more sensitive to NSAIDs than dogs due to deficient glucuronidation.
Concurrent dehydration, steroids, or ACE inhibitors markedly increase toxicity risk.

Basis and limits

Calculation basis: Dose (mg/kg) = total dose ingested (mg) / body weight (kg).
Assumed toxic thresholds: defaults are commonly cited GI/renal toxicity thresholds. Adjust in assumptions to match specific references.
Risk modifiers: concurrent steroids increase GI ulceration risk; ACE inhibitors/diuretics and dehydration increase renal risk; cats have heightened CNS sensitivity to ibuprofen.
Scope: this tool estimates exposure. It does not replace toxicology consultation or clinical judgment.

Formula audit trail

1. Convert weight to kg if entered in pounds (lb × 0.453592).

2. Dose (mg/kg) = total dose ingested (mg) / body weight (kg).

3. Compare to species- and drug-specific toxic threshold from assumptions panel.

4. Apply risk modifiers based on concurrent medications and hydration status.

Calculation steps will appear here for verification.

Related tools

Last reviewed: May 2026

Sources: Plumb's Veterinary Drug Handbook; ASPCA Animal Poison Control Center

NSAID toxicity calculator

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