Rimadyl is the brand name for the anti-inflammatory pain drug carprofen. It is given to dogs to help relieve pain, particularly arthritis pain, and bring down a fever. This type of pain drug is a nonsteroidal anti-inflammatory drug (NSAID) in the same family as ibuprofen and naxoproxen. Those drugs can be lethal to dogs, because a Rimadyl overdose in dogs is a medical emergency according to "The Pill Book Guide to Medication For Your Dog and Cat."
The normal dosage of Rimadyl is 2 mg for every pound that the dog weighs, according to Rimadyl's manufacturer, Pfizer. "The Pill Book Guide to Medication For Your Dog and Cat" notes that dogs have been tested taking 20 mg per pound for 14 days and rarely suffered from overdose symptoms. However, giving more than the veterinarian's prescribed dose is not recommended.
Symptoms of dogs suffering a Rimadyl overdose include black feces that resemble tar, nausea (where a dog often licks its lips and cringes), vomiting, loss of appetite, increase in thirst, urinating more frequently, swelling of the abdomen and tenderness of the abdomen, according to veterinarian Dr. Anne Marie Manning. The dog will not want the abdomen or belly area touched and may not be able to lie down because of the pain.
Rimadyl overdoses can cause bleeding in the digestive tract, which causes the tarlike stools. Rimadyl can also damage the dog's kidneys, which causes the sudden increase in thirst, frequent urination and very pale-colored urine. But the most deadly is liver damage. Signs of liver damage include all of the signs for Rimadyl overdose plus a lack of energy and discoloration of the skin inside of the ears, the whites of the eyes and the gums.
Dogs with Rimadyl overdose need to have their stomachs pumped if they have not already begun vomiting. They need activated charcoal to help absorb the toxin already in the stomach. Then, an antacid such as famotidine (brand name Pepcid AC) is given. To avoid dehydration and kidney damage, the dog will need to be put under anesthesia and fitted with a catheter as well as receive IV fluids. If the dog cannot stop vomiting, than antinausea medication can be given.
Labrador retrievers or Labrador retriever crossbreeds are thought to be more prone to Rimadyl side effects and overdoses than any other dog breed. Labrador retrievers on Rimadyl have been known to die, according to Canada's Guide to Dogs. However, Labrador retrievers are more prone to arthritis than other breeds, so perhaps more Labradors are the breed getting Rimadyl the most and therefore seem to suffer the most side effects.