Rimadyl(®) (carprofen) is a medicine created specifically for treating dogs with osteoarthritis. Much like Previcox, it is an NSAID, and it produces its effects by inhibiting cyclooxygenase (COX). The two forms of cyclooxygenase, COX-1 and COX-2, have different roles in the body – COX-1 is involved with the function of the kidneys and platelets, while COX-2 is mainly involved in the inflammatory response. Because COX-1 is important in the body, and because the main goal when treating arthritis is to reduce inflammation, medicines which spare COX-1 while inhibiting COX-2 are preferred. Rimadyl is thought to be more sparing of COX-1 at therapeutic doses which means dogs are less likely to experience problems with the kidneys, platelets or stomach than with some of the older generation cyclooxygenase inhibitors.

Despite the more selective inhibition of COX-2, carprofen still has the potential to cause side effects, particularly in senior dogs, and should not be given to those with liver or kidney disease. Because of the risk (though rare in healthy dogs) of bad reactions which can lead to death in the most severe cases, we recommend trying natural remedies and supplements before resorting to treatment with this medicine.

Safer Alternative

Rimadyl has been associated with a number of dangerous side effects including death. To treat arthritis naturally and avoid putting your dog at risk, try Arthro-Ionx, a safe and effective remedy for arthritis and joint pain in dogs.

Recommended Dosage

Note: Do not begin treatment with Rimadyl or any other medicine containing carprofen unless a vet has given you permission to do so.

The usual dosage of Rimadyl for relieving pain or treating inflammation in dogs is 2 mg/lb once daily, or 1 mg/lb twice daily. You should round the dosage your dog needs to the nearest half caplet increment. If injecting the drug subcutaneously (under the skin), the dosage remains the same.

carprofen canine dosage chart

Some vets prefer a lower dosage of 1 mg/lb once daily. It’s best to use the lowest dose at which your pet’s symptoms are relieved to lower the risk of adverse effects.

Should I give this medicine with food?

The medicine should always be given with food to help to reduce the risk of vomiting and other gastrointestinal effects. With that said, administering with food does not eliminate the risk completely.

Example: A 25 lb dog could be given 50 mg once daily, or 25 mg twice daily. Some vets may recommend a dose of 25 mg once per day. Always follow the exact recommendation of your vet.

How Safe Is It?

Rimadyl is likely safer for dogs than other NSAIDs like aspirin, and is more sparing of COX-1 than many other drugs of its kind, but it can cause bad reactions. These bad reactions can be severe and there are even reports of dogs dying during treatment.

Dogs may be unsuitable for treatment if they:

  • Have poor liver or kidney function
  • Are old (higher risk of a bad reaction)
  • Have bleeding disorders (e.g. Von Willebrand’s)
  • Have Inflammatory Bowel Disease
  • Are under 6 weeks of age
  • Are pregnant or nursing

Liver disease occurs in around 1 in every 2000 (0.05%) dogs treated with carprofen.

Carprofen has also been shown to affect TSH and total T4 levels in the blood. Interestingly, free T4 seems to remain unaffected, but this should still be taken into consideration when testing thyroid function, and caution is advised.

Guidelines Of Use

Follow these guidelines when treating your dog with Rimadyl:

  • Try natural remedies and supplements first
  • Talk to the vet about the risks and benefits of treatment
  • Tell the vet about any medical conditions affecting your dog and any other medication he is taking
  • Have the vet perform baseline liver and kidney function tests before beginning treatment
  • Monitor liver and kidney function routinely during treatment
  • Avoid use in dogs with kidney disease, liver disease, bleeding disorders or IBD
  • Avoid use in pregnant or nursing dogs, or in puppies under 6 weeks old

As well as monitoring kidney and liver function, Complete Blood Count (CBC) and Uric Acid (UA) blood tests are advised, and may be repeated on a regular basis. Stop use of the medicine for a minimum of 24 hours before switching to a different NSAID.

Warning: Do not give other NSAIDs (such as Deramaxx) in conjunction with Rimadyl as this can increase the risk of stomach ulceration and bleeding.

What Is It Used For?

Rimadyl is used to treat:

  • Pain
  • Inflammation
  • Arthritis

It can be given 2 hours before surgery to control postoperative pain. If carprofen is unsuitable or if your dog only needs pain relief and not inflammation control there are other medicines you can ask your vet about.

Carprofen has also been explored as a treatment for tumors and malignant cells, as the overexpression of COX-2 is thought to affect tumorigenesis.

Side Effects

Rimadyl could cause these unwanted effects:

Most Common

  • Vomiting
  • Diarrhea
  • Loss of appetite

Less Common

  • Changes in behavior
  • Kidney or liver damage
  • Bleeding problems (look out for black tarry stools or blood in vomit)
  • Severe gastrointestinal problems
  • Loss of coordination
  • Seizures

Speak to the vet about any adverse effects your dog experiences during treatment. Signs of liver damage include yellow tinting of the eyes or gums, while kidney damage may result in changes to the frequency of urination.

Even if there are no problems at first your dog could suddenly become ill after months of treatment. Complications related to the medicine could ultimately lead to death in the most serious cases. Animal behaviorist Steve Dale has a good article on his website about the serious side effects of Rimadyl.


Dogs react to this drug in different ways. Some can tolerate high amounts up to 10x the recommended dosage, while others suffer severe reactions. To lower the chance of overdose keep the tablets in a well secured cabinet which can’t be accessed by pets. Always seek veterinary care or call the ASPCA Poison Control Hotline on (888) 426-4435 if you suspect an overdose.


Dr. D. Boothe
Plumb’s Veterinary Drug Handbook (sixth edition)