Can I give Aspirin to my cat?

The short answer: **Almost never** — cats metabolize aspirin 5× more slowly than dogs, and toxicity is cumulative

Cats lack the liver enzyme glucuronyltransferase that safely processes aspirin in humans and dogs. Aspirin's plasma half-life in cats is approximately 45 hours (vs 7–8 hours in dogs and 2–3 hours in humans). This means that even a "low" single dose can accumulate to toxic levels over several days. Modern veterinary medicine has better cat-safe alternatives; aspirin is rarely prescribed today.

When it is (rarely) prescribed for cats

Veterinary cardiologists historically used low-dose aspirin (5 mg every 72 hours) in cats with feline arterial thromboembolism (e.g., from hypertrophic cardiomyopathy). Most clinicians now prefer clopidogrel (Plavix) for feline thromboprophylaxis because of better efficacy and safety profiles. Aspirin in cats should ONLY be prescribed and monitored by a veterinarian — never from owner initiative.

Toxic doses in cats

• >40 mg/kg as a single dose: significant toxicity
• >25 mg/kg daily for several days: cumulative toxicity
• A single 325 mg adult aspirin tablet = 81 mg/kg in a 4 kg cat — 2× the toxic threshold
• Even baby aspirin (81 mg) = 20 mg/kg — dangerous on repeated doses

Signs of aspirin toxicity in cats

• Vomiting (may be bloody)
• Loss of appetite, weight loss
• Lethargy, weakness
• Respiratory depression or rapid shallow breathing
• Hyperthermia (paradoxically)
• Methemoglobinemia (brown-grey gums)
• Heinz body anemia
• Acute kidney injury
• Seizures and coma in severe cases

Emergency treatment