Naproxen Toxicity in Cats

Naproxen is a popular and effective over-the-counter medication available to treat pain and inflammation in people. For cats, naproxen can easily exceed toxic levels. The most common cause of naproxen toxicity is a well-meaning owner who gives the medication without knowing the toxic dose.

The initial toxic effect is bleeding stomach ulcers. In addition to ulcers, increasing doses of naproxen eventually leads to kidney failure and, if left untreated, can be fatal.

What to Watch For


Diagnosis of naproxen toxicity is generally based on physical exam findings and a history of access or exposure to naproxen.

Blood tests are done to determine the overall health of the cat. If naproxen was ingested, blood tests may reveal anemia from a bleeding ulcer or kidney damage.


After one or two days of treatment, repeat blood work may be done to evaluate kidney function after treatment.

Home Care and Prevention

There is no home care for naproxen toxicity. Veterinary care is strongly suggested to treat kidney failure and bleeding stomach ulcers.

While recovering from naproxen toxicity, feeding a bland diet for one or two days is encouraged. Gradually return to a normal diet. Watch for not eating, vomiting or continued black tarry stools.

The best preventative care is to give your cat medications only if directed by your veterinarian. Medications that may be safe for people can be fatal to cats. Also, make sure that all medications are kept out of the reach of inquisitive pets. Keeping medicine safely stored away can prevent many tragedies.

Naproxen toxicity typically results from administration of an improper dose by well meaning owners or acute overdose from curious animals eating large quantities.

Naproxen belongs to a class of drugs known as non-steroidal anti-inflammatory drugs (NSAIDs). The purpose of these drugs is to reduce the pain associated with inflammation. NSAIDs work by inhibiting the production of prostaglandins. There are different types of prostaglandins and, as a class, are responsible for a wide variety of normal body functions. They are present in areas of trauma to help repair damage. They also maintain proper blood flow to the kidneys and protect the stomach lining from the effects of stomach acids.

The primary reason NSAIDs are used is to reduce the presence of prostaglandins in trauma related injuries. Without prostaglandins, there is less inflammation and therefore, less pain. Unfortunately, medicine has yet to make an NSAID that only affects the prostaglandins associated with inflammation. When the prostaglandins for inflammation are inhibited, so are those responsible for normal kidney blood flow and stomach protection. This is the cause of the toxic properties of naproxen in pets.

The toxic signs of naproxen include:

Dogs are particularly sensitive to the stomach ulcer effect of naproxen. Stomach ulcers can occur within 12 hours of ingestion but sometimes can take up to four days. Cats are more sensitive to the kidney effects of naproxen. With massive overdose or ingestion, severe kidney impairment can occur within 12 hours of ingestion but may take up to five days. In severe cases, seizures may occur.

Naproxen can result in stomach ulcers at a dose of 2.5 mg per pound (6 mg/kg) daily. Naproxen can result in kidney failure at a dose of 7 gm per pound (15 mg/kg).

Treatment is based on the severity of the toxicity. Repeated doses of sub toxic levels can eventually result in toxic signs.

If ingestion was recent, administration of activated charcoal can help reduce toxin absorption.

For stomach ulcers

For kidney failure