Short answer: don’t give a dog or cat any human pain reliever unless your veterinarian tells you to. Pet Poison Helpline warns that as little as one 220-mg naproxen (Aleve) tablet can cause very serious illness, including death, even in a large dog — and ASPCA Animal Poison Control Center experts say there is no safe dose of acetaminophen (Tylenol) for cats. If your pet has swallowed one, call your vet, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661 now, before symptoms appear.
This came back into the news in September 2026, when Pet Poison Helpline described a young dog in South Carolina who chewed open a bottle of naproxen during about 15 minutes alone. By the time she reached the clinic, bloodwork already showed kidney damage and anemia from stomach bleeding. She recovered fully after aggressive treatment — IV fluids, stomach protectants and weeks of monitoring — but the helpline’s senior toxicologist said those injuries would have been fatal without it.
Why Human Painkillers Hit Pets So Hard
Drugs like naproxen and ibuprofen (NSAIDs) work by blocking prostaglandins — the same compounds that protect the stomach lining and keep blood flowing to the kidneys. Dogs and cats are far more sensitive to that effect than people, and in dogs naproxen lingers: the Merck Veterinary Manual reports a half-life of about 74 hours in dogs, because the drug is recycled through the liver and gut instead of being cleared.
Cats are more vulnerable still. They have limited ability to process these drugs through glucuronidation, one of the liver’s main clearing pathways. That is why the ASPCA’s poison-control experts describe cats as roughly twice as sensitive to ibuprofen as dogs, why aspirin’s half-life in cats is about 37.5 hours (Merck), and why acetaminophen is so dangerous for them.
How Much Is Too Much? It Depends on Weight
Toxicity is measured in milligrams of drug per kilogram of body weight, which is why one tablet can be trivial for a person and serious for a pet. Veterinary toxicology references put the start of stomach injury from naproxen in dogs at around 5–7 mg/kg, with kidney effects possible from about 13–15 mg/kg (ASPCA poison-control data) and acute kidney failure commonly cited above 25 mg/kg.
Here is what a single 220-mg naproxen tablet works out to — shown only to explain why vets take one tablet seriously, not as a safe-dose guide:
| Dog’s weight | One 220-mg tablet equals | Where that falls |
|---|---|---|
| 10 lb (4.5 kg) | ~48 mg/kg | Well past the kidney-injury range |
| 20 lb (9.1 kg) | ~24 mg/kg | Near the level linked to acute kidney failure |
| 40 lb (18.1 kg) | ~12 mg/kg | Past the stomach-injury range; near kidney effects |
| 70 lb (31.8 kg) | ~7 mg/kg | At the stomach-injury range |
| 100 lb (45.4 kg) | ~5 mg/kg | At the lowest published stomach-injury level |
For ibuprofen, the ASPCA’s published poison-control figures describe vomiting and stomach pain from single doses around 25 mg/kg, kidney failure above roughly 175 mg/kg, and seizures above 400 mg/kg in dogs — with cats affected at about half those doses. One 200-mg tablet is about 22 mg/kg in a 20-lb dog and 44 mg/kg in a 10-lb cat.
Acetaminophen is different: Merck notes dogs rarely show signs below about 100 mg/kg, but for cats, signs have appeared at around 10 mg/kg — roughly one-seventh of a single 325-mg tablet for an average 10-lb cat.
The Four You’re Most Likely to Have at Home
- Naproxen (Aleve, some store brands): long-acting in dogs; stomach ulcers and bleeding, then kidney injury. One tablet matters.
- Ibuprofen (Advil, Motrin): the NSAID pets are most often exposed to, per ASPCA poison-control data; vomiting, bloody or black stool, kidney injury, and seizures at very high doses. Ferrets are especially sensitive.
- Acetaminophen (Tylenol, and many “cold & flu” and combination products such as Excedrin and Percocet): in cats, it damages red blood cells within hours — look for brown or muddy-colored gums, labored breathing, and swelling of the face or paws. In dogs, large amounts injure the liver.
- Aspirin and salicylates: besides tablets, Pet Poison Helpline lists Pepto-Bismol, oil of wintergreen, and rub-on products like Bengay and Icy Hot as sources. Cats are much more sensitive than dogs.
Signs to Watch For (But Don’t Wait for Them)
Vomiting (sometimes with blood), black or tarry stool, not eating, belly pain, lethargy, pale gums, drinking or urinating much more or much less than usual, and — in severe cases — wobbliness or seizures. In cats that have had acetaminophen: brown-tinged gums, fast breathing, and a swollen face or paws.
The timing is the trap. ASPCA data on naproxen show stomach signs usually appear within 2–24 hours and kidney effects within 24–48 hours. By the time kidney values rise, the easiest treatment window has closed.
What Happens at the Vet
If the ingestion was recent, the vet may make your pet vomit and give activated charcoal to limit absorption. From there, treatment depends on the drug and dose: stomach protectants for one to two weeks, IV fluids for at least a couple of days to protect the kidneys, repeat bloodwork, and — for acetaminophen in cats — an antidote (N-acetylcysteine). Large ingestions sometimes need specialist care such as plasma exchange.
The outlook is good when care starts early. In a study of 434 dogs treated for ibuprofen, carprofen or naproxen poisoning at four US veterinary teaching hospitals, 99% survived (Journal of Veterinary Internal Medicine, 2023). Dogs that reached care later — more than about 7.5 hours after ingestion — were more likely to develop kidney injury.
Cost: no poison center publishes average bills. One insurer’s example emergency (exam, bloodwork, induced vomiting, charcoal, two days of IV fluids and monitoring) came to about $2,075, and costs vary widely by region and whether intensive care is needed. The poison hotlines charge a consultation fee — Pet Poison Helpline lists $89 per incident, including follow-up calls with your vet; the ASPCA says a fee may apply. If you have pet insurance, check whether poisoning treatment and the hotline fee are covered — see our guide to what pet insurance actually costs per month.
What Vets Prescribe Instead
If your dog is stiff or sore — often arthritis in an older dog — there are safer, pet-specific options. The FDA lists carprofen, deracoxib, firocoxib, grapiprant and meloxicam as NSAIDs approved for dogs. For cats the list is much shorter: meloxicam and robenacoxib are approved only for short-term use around surgery, and the FDA warns that repeated doses of meloxicam in cats can cause kidney failure. Newer monthly antibody injections exist for osteoarthritis pain in cats and dogs. Even these need a vet’s dosing and monitoring — pet NSAIDs can also cause stomach and kidney problems if misused. Non-drug support matters too: weight control, joint supplements, and home changes like ramps and rugs.
Hidden Sources People Forget
- Pain creams, gels and patches. The FDA warned that cats became ill or died after owners used compounded pain creams containing flurbiprofen; the ASPCA notes cats can be exposed just by licking an owner’s skin. Diclofenac gels are another source.
- Combination cold and flu medicines, which often contain acetaminophen.
- Dropped pills, weekly pill organizers, and bags left on the floor.
- Flavored chewables — the ASPCA’s 2025 poison report notes they make it more likely a pet eats a whole container.
Over-the-counter medications and supplements were the single largest category of pet poisonings the ASPCA handled in 2025, at 16.9% of more than 376,000 cases.
The Bottom Line
Human painkillers are among the most common and most preventable pet poisonings. Keep them in closed cabinets, never share your own medicine to “take the edge off” a pet’s pain, and treat any swallowed tablet as an emergency phone call rather than something to watch and wait on. Caught early, most pets recover well.
This article is for informational purposes only and does not replace guidance from your veterinarian. If you think your pet has eaten medication, call your vet or an animal poison control line immediately.
Sources
- Pet Poison Helpline — “Relaxing Shower Turns to Puppy Panic” (Toxin Tails, September 2026) and Naproxen, Acetaminophen, Aspirin toxin pages; fees
- dvm360 — Naproxen ingestion puts dog at risk of kidney injury and GI bleeding, September 9, 2026; Toxicology brief: naproxen toxicosis in dogs (ASPCA APCC), 2013
- Merck Veterinary Manual — Toxicoses from Human Analgesics in Animals, reviewed July 2024, updated May 2025
- ASPCA Animal Poison Control Center — Ibuprofen toxicosis brief (Veterinary Medicine, 2004); Top 10 Toxins of 2025, March 2026; ASPCA Poison Control
- Lynch et al. — NSAID toxicosis in 434 dogs, Journal of Veterinary Internal Medicine, 2023
- U.S. FDA — Get the Facts about Pain Relievers for Pets; Pet exposure to topical pain medications containing flurbiprofen
