Naproxen Toxicity 

Naproxen, commonly known as Aleve, is an over-the-counter NSAID that alleviates pain, inflammation, and fever in humans. These medications are generally safe and effective in treating discomfort. Unfortunately, naproxen is poisonous to both dogs and cats. Just one tablet can cause poisoning and even death in a large pet.  

Dangers of Naproxen 

As a pet owner, seeing your pet in pain is heart breaking, but you must steer clear of providing them human NSAIDs as it can only make it worse. Naproxen is a long-acting drug which means it stays in the system for an extended period of time and can take effect within 1 to 2 hours after ingestion. Severe symptoms can arise from just one tablet of Aleve. You must talk to your veterinarian first before attempting to give your pet any medication. Your veterinarian can determine what is wrong with your pet and prescribe the correct course of treatment, such as pet-friendly medications. 

Naproxen Toxicity Symptoms 

Naproxen poisoning can seem the same as poisoning symptoms from other medications, so you must be vigilant and monitor your pet’s environment and what they eat. Make sure your medications are safely put away so your pet cannot get to it. Potential symptoms of Naproxen toxicity include:  

  • Abdominal pain 
  • Lack of appetite 
  • Weakness 
  • Vomiting 
  • Pale gums 
  • Lethargy 
  • Bloody stools 
  • Diarrhea 
  • Increased drinking and urination due to kidney failure 


If your pet ingested Aleve, you must call your veterinarian and Pet Poison Helpline at (855) 764-7661 for immediate medical attention. Treatment will vary depending on the dosage, your pet’s health and size, and the severity of the symptoms. Activated charcoal may be given to bind the toxins. IV fluids will aid in hydration and flushing the toxins from their system. Your veterinarian may administer medications to counteract the effects of naproxen. You must find treatment immediately so your pet can have a good chance of recovery.