Side Effects of Carprofen for Dogs

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Carprofen is a non-narcotic, non-steroidal anti-inflammatory (NSAID) prescription medicine that helps relieve pain and inflammation in dogs. It is often used for dogs with symptoms of arthritis or to control pain following a surgery. It is in the propionic acid class along with ibuprofen, naproxen, and ketoprofen. Pfizer originally produced it to be used in human medicine, it was on the market for human use from 1985 to 1995. Carprofen was voluntarily pulled from the market for human use by Pfizer on commercial grounds. A few of the side effects that carprofen may cause for dogs are lack of appetite, jaundice, and hematuria.

Carprofen is prescribed from Veterinarians for two main reasons:

Carprofen does not cure arthritis, it is used to alleviate or reduce the discomfort and signs of pain associated with arthritis. This medicine works for dogs by treating inflammation, lowering fever, and reducing pain, it is similar to an ibuprofen for dogs.

How is Carprofen Administered to Dogs?

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Carprofen for dogs must be prescribed by a veterinarian. It is available in 25 mg, 75 mg, and 100 mg flavored tablets or chewables that are administered orally, preferably with food. Administering Carprofen to dogs with food can help reduce the likelihood of the dog getting an upset stomach. The recommended dose is 2 mgs per pound of body weight once a day or 1 mg per pound of body weight given twice a day.

Therefore, if your dog weighs 25 pounds then the recommended dose would be 50 mgs once a day or 25 mgs twice a day. The veterinarian will decide if the medication should be given once a day or if the dose should be split and given twice a day.  If prescribed for managing postoperative pain, it should be given approximately 2 hours before the operation. Consult your veterinarian if you observe any adverse or potentially harmful reactions. In this case Carprofen may not be the right medication for your dog.

Carprofen Precautions and Drug Interaction

  • Dogs with hypersensitivity or allergies to other NSAIDs should not take Carprofen
  • May increase adverse reactions if taken along with other NSAIDs (like aspirin)
  • May increase adverse reactions if taken along with steroids (like corticosteroids and cortisone-like drugs)
  • May increase adverse renal reactions if taken with nephrotoxic medications
  • Effectiveness may be reduced if given in the presence of ACE inhibitors, not suggested to use concurrently
  • May increase the activity of anticoagulant medications, not suggested to use concurrently
  • Should be very careful if given to dogs with bleeding disorders, cardiovascular diseases, dehydration, gastrointestinal diseases, hypoproteinemia, or renal disease.
  • Carprofen should not be giving to pregnant or nursing dogs

How Does Carprofen Work?

The mechanism of action of Carprofen is not completely understood, it is suspected to be associated with the inhibition of cyclooxygenase activity, similar to how other NSAIDs function.  Cyclooxygenase (COX) enzymes catalyze the conversion of arachidonate to prostaglandin H2, which is a precursor for many important biological molecules, particularly prostaglandins. Prostaglandins play a large role in modulating inflammatory responses. Drugs that act as inhibitors of COX activity are said to be NSAIDs.

Some NSAIDs are selective in which COX enzyme they interact with. There are two distinct cyclooxygenases: COX-1 and COX-2. The COX-1 enzyme synthesizes prostaglandins necessary for normal gastrointestinal and renal function. The inhibition of COX-1 enzymes is suspected to be associated with gastrointestinal and renal toxicity. The COX-2 enzyme synthesizes prostaglandins involved in inflammation. The inhibition of COX-2 enzymes provide anti-inflammatory activity.

Although, an in vitro study (tested outside of the organism ie: in a dish or test tube) has shown that Carprofen has specificity for COX-2 in canines, the specificity may vary from species to species. There have been no clinical or in vivo studies (tested within an organism) done that prove Carprofen has selective specificity to COX-2.  

Side Effects of Carprofen in Dogs

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No clinically significant adverse reactions were reported during the investigational studies of osteoarthritis or surgical pain nor during the clinical field studies of osteoarthritis. Each of these studies administered Carprofen daily at 2 mg per pound of body weight. All adverse reactions listed below were reported after the FDA approved Carprofen. Since it is still not fully understood how NSAIDs like Carprofen work, the drug may affect a multitude of signaling pathways and cellular mechanisms that we are not aware of.

Most of the time, dogs will only have mild side effects, if any. The most common side effects of Carprofen for dogs include upset stomach, diarrhea, and ulcers. It’s important to look at all the symptoms to determine what part of your dog is being affected by the medication.

Gastrointestinal Effects of Carprofen for Dogs

These are side effects that have to do with issues involving the stomach and small intestines. Gastrointestinal effects are most likely due to the drug cross-inhibiting the COX-1 enzyme, which synthesizes prostaglandins necessary for normal gastrointestinal and renal function. Although Carprofen has specificity for COX-2, the two enzymes are almost identical and cross-reaction can occur. The majority of these side effects subsided once treatment was discontinued.

  • Vomiting
  • Diarrhea— loose or watery bowel movements
  • Constipation— difficulty with passing bowel movements
  • Lack of appetite
  • Melena— stools appear black and tarry due to the presence of digested blood in feces, which is caused by gastrointestinal bleeding
  • Vomiting Blood –  caused by gastrointestinal bleeding
  • Gastrointestinal ulceration— formation of ulcers due to the thinning of mucosal lining of the stomach
  • Pancreatitis— inflammation of the pancreas

Hepatic Effects of Carprofen

These side effects occur from issues related to the liver and its function. Liver damage from Carprofen is seen in about 0.02% of dogs. Labrador Retrievers account for approximately one-fourth of all adverse hepatic reactions. You may be able to catch early signs of liver damage by getting blood tests regularly to check for elevated liver enzymes.

  • Inappetence—lack of appetite, generally the first sign of hepatopathy (liver dysfunction)
  • Vomiting
  • Jaundice—yellow discoloration of mucous membranes (gums, nostrils, genitals, and other areas) due to a high concentration of bilirubin, aka hyperbilirubinemia
  • Hepatotoxicity—drug-induced liver damage that can lead to acute and chronic liver disease (occurs in 1.4 out of 10,000 dogs)
  • Abnormal liver function tests, including hepatic enzyme elevation, bilirubinuria, and hypoalbuminemia

Urinary Effects Of Carprofen For Dogs

Adverse reactions that lead to urinary issues are most likely due to issues affecting the kidneys since those are part the urinary tract system.

  • Hematuria— blood in urine
  • Polyuria— increased frequency of urination
  • Polydipsia— excessive thirst
  • Urinary incontinence— involuntary leaking urine
  • Urinary tract infection— all previously listed conditions are symptoms of a UTI
  • Azotemia— high levels of blood nitrogen
  • Tubular abnormalities, including acute tubular necrosis, acute kidney failure