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Rimadyl and dogs

Posted Aug 05 2008 3:21am

Rimadyl (Carprofen), introduced by Pfizer Pharmaceuticals in January 1997, has proven to be a successful means of relieving arthritis symptoms in dogs. Many users feel it has vastly improved the quality of their dogs’ lives and, in some cases, even extended their lives. However, there is a growing body of evidence showing that the drug has serious side effects. Some dogs have died due to the unexpectedly rapid onset of side effects, and/or because the drug’s side effects were not recognized by the attending veterinarian who did not take appropriate action.

It was not at first clear that Labradors were particularly susceptible to Rimadyl toxicity, since Labradors, more than other breeds, have joint problems and are given Rimadyl for relief. However, Pfizer’s report on side effects that occurred during the drug’s initial post-approval phase states, “. . . approximately one fourth of all hepatic reports were in Labrador Retrievers.” This appears to be an alarmingly high incidence and should guide your choice of using Rimadyl if your dog is a Lab.

Many breeds, including Labrador Retrievers, are represented in the population that has experienced side effects or a fatal outcome from Rimadyl. Although the deaths and side effects reported on this site are only a representative sample, you will find many different breeds named in the reports.

Cautions about Administering Rimadyl

Veterinarians are advised to pre-screen a dog before prescribing Rimadyl and then to re-test and closely monitor the dog for possible toxic reactions at periodic intervals. The Senior Dogs Project has had repeated reports from people who have discussed Rimadyl with their vets and found that their vets were not aware that pre-screening and regular monitoring were suggested (but not required) by Pfizer. In many cases, the vets were not aware of the side-effects of the drug, or the period during which the side-effects might occur. (Note: Although originally this period was thought to be two to six weeks, adverse reactions have been reported after a matter of hours.)

Carprofen is not recommended for animals with known bleeding disorders and should not be used if a dog has pre-existing liver disease, inflammatory bowel disease, or a known tendency towards gastrointestinal ulceration.

Rimadyl should never be given along with any other non-steroidal anti-inflammatory drug (NSAID) such as aspirin, or along with any corticosteroids such as prednisone, prednisolone, or dexamethasone. The University of California at Davis recommends a two week “rest” period when changing from any NSAID to carprofen or from carprofen to another NSAID.

If Carprofen is used concurrently with phenobarbital, it is especially important that appropriate liver monitoring be performed. (Mar Vista Animal Hospital recommends bile acids testing every 6 months for dogs on phenobarbital.) ACE inhibitors such as enalapril or captopril may not be as effective in the presence of carprofen. (ACE inhibitors are used in the treatment of hypertension or heart failure.) It is also advised that the drug not be given to pregnant or nursing females because it has not been tested with them.

In cases where dogs have had toxic reactions and recovered, continued monitoring over an extended period (perhaps as long as a year) may be advisable because the long-term effects of liver or other organ damage are not yet known.

Deciding to Use Rimadyl

Carefully decide whether Rimadyl is appropriate for your dog by weighing the benefits against the risks. Keep in mind that it has been widely reported that many veterinarians are not fully informed about this drug. As Stephen Fried so eloquently summarizes in his book, Bitter Pills: “It’s a question of whether the potential benefit is worth the risk and whether the patient understands that risk — which depends on whether the doctor knows enough about the drug to really explain the risk.”

If you decide your dog may benefit from Rimadyl and it is worth the risks involved, tell your vet that you want to determine the lowest possible dosage that can be used to obtain relief. Although the recommended dosage is 1mg/pound of weight twice per day, your dog may get relief at a lower dosage. A lower dosage could be instrumental in avoiding toxicity (although this is not guaranteed). In addition, your vet may recommend that Rimadyl be used for short periods (several weeks), or intermittently, as needed, with time off (several weeks) to give the dog’s liver time to recover.

Insist on baseline tests and continued monitoring of the relevant functions during the entire time your dog takes the drug. Pfizer only recommends this and does not indicate that it is a requirement.

To avoid the gastric upset that occurs in some dogs, the drug should be given with food. Pepcid may also be used concurrently to control gastric upset.

As soon as your dog begins Rimadyl therapy and during the entire time he takes it, watch for the following symptoms, all signs of potential life-threatening reactions to the drug:

* loss of appetite

* change in drinking habits (refusal to drink or increased water consumption)

* unusual pattern of urination, blood in the urine, sweet-smelling urine, an overabundance of urine, urine accidents in the house

* vomiting

* diarrhea

* black, tarry stools or flecks of blood in the vomit

* lethargy, drowsiness, hyperactivity, restlessness, aggressiveness

* staggering, stumbling, weakness or partial paralysis, full paralysis, seizures, dizziness, loss of balance

* jaundice (yellowing of the skin, mucus membranes and whites of the eyes)

In the presence of any of these symptoms, IMMEDIATELY STOP the drug and take your dog to the vet. The earlier you catch the problem, the better the chances of complete recovery.

It will be helpful to Pfizer and may help to save your or another dog’s life if you report any negative reactions your dog has or had when taking Rimadyl. You need only have a suspicion that Rimadyl is implicated. You may call Pfizer at 1-800-366-5288 and the FDA at: 1-888-332-8387 (or 1-888-FDA-VETS). For step-by-step instructions, click on “If You Suspect Your Dog Has Had an Adverse Reaction to Rimadyl” in the navigation bar at the left.



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