Osteoarthritis in dogs can cause a great deal of pain and discomfort to our furry friends. One way to reduce the pain caused by arthritis is the use of anti-inflammatory medications.
Non-steroidal anti-inflammatory drugs (NSAIDs) are the most prescribed pain medications for dogs with osteoarthritis. NSAIDs are known for reducing pain, inflammation, and fever.
Aspirin is the best known NSAID which has been used for a long time both on dogs and people for pain relief. Aspirin is not prescribed as much for dogs these days because safer and better drugs (such as Rimadyl) are available.
While these newer drugs appear to be safer for most dog patients, it is still important to remember that any drug can cause adverse reaction. Therefore, as dog parents, we should get more knowledgeable about these canine pain medications.
How Do NSAIDs Work
Arachidonic acid is a fatty acid essential in a dog’s diet and found in cell walls. When inflammation begins, arachidonic acid is broken down by cyclooxygenase (COX) into prostaglandins and by lipoxygenase into leukotrienes.
Generally speaking, prostaglandins promote swelling and increase nerve sensitivity to pain. Leukotrienes attract inflammatory cells that worsen the inflammation and add to nerve sensitivity.
Anti-inflammatory drugs work to block the COX and/or lipoxygenase from forming prostaglandins and/or leukotrienes, thereby reducing the pain, swelling, and other symptoms associated with inflammation.
There are at least 2 forms of COX (called COX-1 and COX-2). COX-1 is normally present in many tissues, and inflammation causes COX-2 levels to rise.
COX-1 produces prostaglandins that help protect the stomach, kidneys, and blood vessels. COX-2 produces prostaglandins that are associated with pain and inflammation.
The ideal anti-inflammatory drug, therefore, should be “COX-2-specific”, “COX-2-selective”, or “COX-1-sparing”. That is, they should only select and block COX-2 so that prostaglandins that are associated with pain and inflammation are not produced; yet at the same time COX-1 is spared so that production of the prostaglandins that help protect the stomach, kidneys, and blood vessels is not disrupted.
Aspirin is not COX-2-selective and that explains why aspirin can reduce pain but may also cause an upset stomach.
Newer NSAIDs such as Rimadyl are COX-2-selective; therefore they are considered safer and better for the patients.
Rimadyl for Dogs – A Newer Veterinary NSAID
Carprofen is an NSAID of the COX inhibitory family and is marketed under the brand name Rimadyl manufactured by Pfizer.
Rimadyl inhibits COX-2 more than it does COX-1, so it is considered a COX-2-specific NSAID. It is primarily used to relieve pain associated with osteoarthritis in dogs (but not for cats).
Rimadyl gets metabolized in the liver, and is about 80% eliminated in the feces after liver biotransformation and the remaining 20% is passed in the urine.
Rimadyl for dogs comes in chewable tablets and caplets and is given orally with or without food. Dosage is 1 mg/lb twice a day. The drug’s peak effect occurs one to three hours after ingestion.
Potential Side Effects of Rimadyl for Dogs
Rimadyl should not be given to dogs with previous sensitivity to it or dogs who have shown an allergic reaction to other NSAIDs.
Although a COX-1-sparing NSAID, Rimadyl does have possible effects on prostaglandins that help protect the stomach, kidneys, and blood vessels. Therefore, if your dog is on this medication, you should observe your dog carefully for possible problems of:
- the kidneys: such as frequent water intake and excessive urination;
- the stomach: such as stomach upset, stomach ulcers, appetite loss, vomiting, and diarrhea.
Some dogs, especially Labrador Retrievers, show serious liver problems after taking Rimadyl, although such cases are rare. Signs of liver problems include:
- Jaundice (yellowing of the gums, skin, or eyes)
- Weakness and lethargy
- Hot spots
In most cases, if a dog starts showing side effects, stopping the drug right away and treating if necessary usually end the complications. Do not substitute Rimadyl with another medication without consultation with your veterinarian.
The drug Carprofen has not been tested thoroughly in breeding animals so it should not be used on pregnant or lactating female dogs or to young puppies.