Carprofen

  Carprofen (marketed as Rimadyl) is a non-steroidal anti-inflammatory drug that is used by veterinarians as a supportive treatment for the relief of arthritic symptoms in geriatric dogs. It can be used both short term, for joint pain or post-operative inflammation, or long term.

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Administration

Carprofen is available in 25, 75 and 100 mg tablets, and in injectable form^[1]. The UK has 50 mg tablets as opposed to 75 mg tablets. The usual dosage is 1mg per pound^[2]. In Australia it is marketed as Norocarp in 20 mg and 50 mg tablets or in injectable liquid at 5.0% w/v, for Cattle and canines^[3].

Health issues

Although most dogs respond well to carprofen, it is capable of causing liver toxicity in some animals, and in the early days of introduction there were significant anecdotal reports of sudden animal deaths arising from its use.

It could often not be determined to what extent any of these were carprofen-related however. Indeed, many may not have been connected to use of the drug, as carprofen is often prescribed to older or sick animals, or in cases of significant pain and illness.

Several years later, a more realistic view is that it is safe and tested for the vast majority of animals, however some will react, and therefore regular blood tests (monthly, or at least twice a year) are often recommended if an animal is to be placed on carprofen for long term use. These tests check for liver toxicity byproducts, and confirm that the animal is not suffering an adverse reaction.

For some reason during the first drug trials, black Labrador Retrievers were more likely to exhihbit serious side effects and adverse reactions like liver problems than other test subjects when on it long-term (as for pain relief from degenerative joint disease).^[4] Whether this is because of a specific sensitivity unique to the breed or simply because labradors, being one of the more popular breeds of dog and one prone to joint issues, were over-represented in the study remains unknown. Some veterinarians choose to err on the side of caution and prescribe Deramaxx to these dogs instead. However others report no serious side effects in their Labrador patients prescribed the medication.

This medication has been found to be deadly for some dogs, as witnessed by the FDA receiving more than 6,000 bad reaction reports about the drug manufactured by Pfizer. As a result, the FDA requested that Pfizer advise consumers in their advertising that death was a possible side effect. Pfizer refused and pulled their advertising, however they have included "death" as a possible side effect on the drug label. Plans call for a "Dear Doctor" letter to be issued to veterinarians and a safety sheet will be attached to pill packages.

Pfizer acknowledges a problem with some dog owners, especially the consumer group which mounted a campaign dubbed BARKS, for Be Aware of Rimadyl's Known Side-effects (including loss of appetite, wobbling, vomiting, seizures and severe liver malfunction). The drug company is reported to be contacting pet owners who have told their stories on the Internet, and is offering to pay medical and diagnostic expenses for some dogs who may have been harmed by Rimadyl.

General symptoms to watch for include:

• Loss of appetite
• Vomiting
• Diarrhea
• Increase in thirst
• Increase in urination
• Fatigue and/or Lethargy
• Loss of coordination
• Seizures

Other symptoms which can indicate a problem, and which are worth raising with a vet include excessive drinking or urination, blood or dark tar-like material in urine or stools, jaundice (yellowing of eyes), unusual lethargy and so on.

Human usage

Carprofen was previously used in human medicine for over 10 years, in doses of 150 to 600 mg per day. It was generally well tolerated, with the majority of adverse effects being transient and mild, such as gastro-intestinal pain and nausea, similar to those recorded with aspirin and other non-steroidal anti-inflammatory drugs.

It is no longer marketed for human usage, after apparently being withdrawn on commercial grounds [3].

References

• http://www.pgaa.com/canine/health/rimadylwarning.html