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.
Carprofen is prescribed from Veterinarians for two main reasons:
- Chronic pain management for dogs with osteoarthritis
- Postoperative medication to treat pain and inflammation in dogs following a surgery
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?
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
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.
- 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)
- 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, and glycosuria
- Glomerular disease
Neurologic Effects of Carprofen
Involve any effects on the nervous system, including the spine and brain. Catching these symptoms involves closely monitoring your dog while they are taking Carprofen. It’s unknown why adverse neurological reactions may occur, but there have been a few reports of it happening.
- Ataxia— loss of balance and coordination of limbs, head, and/or trunk
- Paresis— partial paralysis
- Paralysis— loss of ability to move
- Seizures— sudden surge of electrical activity in the brain causing convulsions throughout the body
- Vestibular signs— loss of ability to balance, symptoms include walking in circles, head tilting, stumbling, falling, etc
Behavioral Effects of Carprofen For Dogs
Some of these symptoms may come from discomfort stemming from another side effect and may be the first signal to start watching your dog more closely. Other behavioral side effects may be from the drug itself. Associated behavioral side effects disappeared once treatment is discontinued.
Hematologic Effects of Carprofen
Disorders and diseases that affect the blood.
- Immune-mediated hemolytic anemia— very low red blood cell count or improperly functioning red blood cells
- Immune-mediated thrombocytopenia— when dog’s body attacks its own blood platelets, this can lead to bruising, bleeding, anemia, etc
- Blood loss anemia— very low red blood cell count, possibly from losing too much blood in vomit, stools, urine, etc
- Epistaxis— nose bleeds
Dermatologic Effects of Carprofen For Dogs
This affects a dog’s skin, nails, and hair.
- Pruritus— desire to itch, scratch, and chew on skin causing inflamed skin
- Increased shedding
- Hair loss
- Pyotraumatic moist dermatitis— raw, painful, and irritated skin lesions
- Necrotizing panniculitis/vasculitis— cell death of inflamed fatty tissue under the skin/cell death of inflamed blood vessels
- Ventral ecchymosis— abdominal bruising
Immunologic Effects or Hypersensitivity
These are signs that your dog may be allergic or sensitive to Carprofen. If these symptoms occur, consult your veterinarian immediately about future actions.
- Facial swelling
- Erythema— redness of skin
There are rare situations in which death has been associated with the adverse reactions.
Common Symptoms of Carprofen Overdose in Dogs
- Bloody vomit
- Black-tarry stool
- Inappropriate urination or thirst
- General malaise
- Abdominal pain
Treatment for Carprofen Overdose
- Induce vomiting if ingestion was within 4 hours
- Stomach pumping
- Administer activated charcoal slurry
- Supportive care
- Perform baseline blood values, including CBC and chemistry
Reported Issues and Lawsuits with Carprofen For Dogs
On June 5th, 2009 Sophie, a golden retriever with an injured knee, went to an Aspen Meadow Veterinary Specialist to have knee surgery. The surgery occurred without any complications. Unfortunately Sophie died late July 2009 after taking Rimadyl, the Pfizer brand name of Carprofen, to recover.
Chris Cooper, one of Sophie’s owners, was directed by their veterinarian to administer Rimadyl twice a day to Sophie. After about a week, Sophie stopped eating and began vomiting. Cooper was directed to stop giving Rimadyl to Sophie, but it was too late by this point since she possibly had Rimadyl toxicity. Sophie was brought back to Aspen Meadow to be hospitalized for liver failure caused by Rimadyl toxicity. After 13 days of supportive therapy and treatment, Sophie returned home but continued to vomit and have inappetance. She was rehospitalized and underwent biopsy surgery, but unfortunately on July 26th 2009 Sophie passed.
In 2011, Christopher Cooper and Shelley Smith filed a lawsuit against Pfizer and won, the settlement terms are not disclosed. They didn’t sue for monetary gain, but to raise awareness of the dangers of using Rimadyl. They have created brochures to distribute to organizations and people about Rimadyl to prevent the same thing happening to someone else’s dog.
Montana, a 6 year old husky, was prescribed Rimadyl to treat his stiff legs. Rimadyl worked for Montana at first, but then his owner Angela Giglio noticed that he began losing his appetite. Shortly after inappetance, Montana developed ataxia and vestibular signs indicating neurological issues. Eventually, he couldn’t walk at all and had to be put down. Montana’s autopsy showed that his liver had been damaged due to adverse reactions to a drug. Angela Giglio reported this to Pfizer and the FDA whom tried to pay her off with a measly $440 to not say anything about the possibility that Rimadyl caused Montana’s paralysis.