The Hidden Dangers of NSAIDS (Rimadyl) And Your Dog

Written by Dogs Naturally Magazine on 

NSAIDs, (or Non-Steroidal Anti-Inflammatory Drugs), are commonly used for the treatment of pain and inflammation. There are plenty of prescription NSAIDs for animals, as well as over-the-counter products such as Tylenol, Aspirin, Ibuprofen, Naproxen, and more.

Most medicine cabinets have some sort of NSAID in them and we generally consider them to be safe for us and for our pets.

NSAIDs stand for non-steroidal anti-inflammatory drugs. These medications alleviate the pain and the inflammation caused by dog arthritis. They do this by inhibiting the pro-inflammatory enzyme prostaglandin. Unfortunately, when NSAIDs suppress the inflammatory properties of prostaglandin, they also suppress the enzyme’s other functions.

Prostaglandin is any enzyme important to many bodily processes. The enzyme is responsible for maintaining the blood circulation in the kidneys. It also assists in the production of blood platelets.

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NSAID Toxicity

When NSAIDs inhibit the effects of prostaglandins, it can cause toxicity. NSAID toxicity can be dangerous, and if left unchecked, it can be fatal. Vets are obliged to inform their clients about NSAID toxicity but this doesn’t always happen so dog owners should learn more about the treatments being administered to their dog.

NSAIDs can cause ulcers because prostaglandins are an important component of the protective lining of the stomach and upper intestine. Signs that your dog might be suffering from ulcers caused by NSAIDs are vomiting, change in appetite and blood in the stool. When these symptoms are observed, this is an emergency situation.

The kidneys are dependent on prostaglandins which ensure that enough blood reaches the kidneys. When there is too much NSAID in your dog’s system, this can potentially reduce the blood flow to the kidneys, compromising their ability to function. If you notice any changes in your dog’s behavior or physical condition, it would be best to visit a vet so that a blood test can be performed to check for kidney damage.

Like most drugs, NSAIDs will negatively affect liver function. NSAIDs can cause hepatitis, an inflammation of the liver. Symptoms include an enlarged liver, abdominal pain, fatigue, loss of appetite, nausea, vomiting and jaundice (yellowing of the skin and the whites of the eyes). NSAIDs can also cause acute liver failure. In a short period of time, the liver stops functioning, causing pain, nausea, vomiting, sleepiness, muscle tremors, disorientation or confusion and jaundice. Ibuprofen has been linked to vanishing bile duct syndrome, a condition in which the bile duct is destroyed. Symptoms include jaundice, itching, dark urine and pain. The mechanism of the condition is not clear, but the condition can be so serious that the liver is severely and permanently damaged.

Dogs taking NSAIDs should be tested regularly for liver enzyme levels.

Prescription NSAIDs

Pfizer pioneered the market for dog painkillers when it introduced Rimadyl in 1997. Nearly 15 million dogs have taken it, many for pain from degenerative joint disease, or osteoarthritis.

Rimadyl now has a few competitors with more likely. The market for dog arthritis pain medications tops $130 million a year and is growing about 13% a year, consulting firm Wood Mackenzie says.

But in the first eight years after the introduction of these drugs, Food and Drug records show 3,200 dogs have died or been put down after taking the drugs. Almost 19,000 dogs had bad reactions to them.

The FDA says the drugs are safe, if properly used. Drug makers say fewer than 1% of dogs have bad reactions to them….yet the reactions are likely under-reported as research in humans shows that up to 15% of humans show elevated liver enzymes when on NSAIDs.

Novartis analyzed 1,680 Deramaxx adverse-event reports, including 1,257 osteoarthritis cases. In 59% of osteoarthritis cases, dogs received doses in excess of the approved dose.

In 28% of all the adverse events, the dog was also on another drug, often aspirin. “This is a definite no-no because mixing can cause serious adverse events,” Novartis’ David Stansfield says.

Dogs should also be checked before and after receiving NSAIDs, says veterinarian Wayne Randolph of Flemington, N.J. Before he puts dogs on NSAIDs, he does blood work, involving 35 tests at a cost of $65, to check a dog’s liver and kidneys, and later repeats the blood work.

The deaths and other adverse events are a reminder that all drugs pose risks, including those for animals. Several million dogs received Rimadyl before its warning label was updated to add mention of death in rare cases. No. 2 pain reliever Deramaxx was marketed for a year before its label was so changed.

Despite stronger warnings and other safeguards, the drugs continue to create controversy. Some dog owners and veterinarians say the drugs are being overprescribed by vets who don’t always give risk information to owners and who, like doctors for humans, are often educated on drugs by pharmaceutical companies.

“There are no safe drugs. There are only safe doctors,” says Robert Rogers, founder of the Critter Fixer Pet Hospital in Spring, Texas. “The large number of adverse events occur with these drugs because veterinarians don’t know how to use them.” Drugmakers share the blame, he says. Their sales representatives often fail to present adequate risk information.

Adverse Events

Through November 2004, the FDA received almost 13,000 adverse-event reports about Rimadyl, far more than for any other dog pain reliever.

Pfizer’s database includes almost 20,000 adverse-event reports. The FDA’s data include those “possibly” or “probably” linked to the drug. Adverse events for all drugs are believed to be under-reported.

Pfizer won’t release Rimadyl’s revenue, but it says Rimadyl has the most reports because it’s the oldest and biggest dog pain reliever.

Deramaxx had been used by about 1 million dogs in the three years folllowing its 2002 launch, owner Novartis says. The FDA’s data included 2,813 adverse-event reports for Deramaxx, including 630 dogs who died or were put down.

Rimadyl, with a generic name of carprofen, originated at Roche Laboratories as an anti-inflammatory drug for people. Deramaxx was developed by Novartis for dogs but was discovered by G.D. Searle, where Celebrex originated.

Deramaxx is a COX-2 inhibitor, like Celebrex and Vioxx, the pain reliever for people withdrawn from the market in September because of heart attack and stroke risk.

Before getting FDA approval, Rimadyl was tested in 549 dogs; Deramaxx in about 700. That’s far fewer than the number of subjects in clinical drug trials for human drugs. Erectile dysfunction drug Cialis, for instance, was evaluated in more than 4,000 patients before it got FDA approval.

Pfizer updated Rimadyl’s label twice, the last time in 1999 noting that death occurred in rare instances. That year, it stopped TV ads. Today’s print ads include the death warning.

Deramaxx took a similar path. It went to market in 2002 with a label saying the drug “was well tolerated” with an adverse event rate comparable to dogs treated with placebos. Once again, adverse events after the drug was sold proved otherwise.

Both drug makers now issue information sheets for dog owners describing the drugs’ risks and proper use. Pfizer even attaches the sheet to Rimadyl bottles. But it may not get to consumers because veterinarians frequently repackage drugs into smaller vials. Marks says risk information is rarely discussed with clients. The FDA has said pet owners often complain about not getting the sheets.

There are many options for your dog’s pain and arthritis that may have the same benefits as NSAIDs without the dangerous side-effects. If you feel your dog must be on an NSAID, be informed about the symptoms of liver disease and make certain your vet is too.

You also want to be careful about the condition your vet is prescribing the NSAID for. It has also been observed that NSAIDs prevent bone fractures from healing. The University Of North Carolina School of Medicine also found that the COX-2 inhibitors not only have an adverse effect on bone healing, they may also impair the healing of ligaments. Please do more research if your vet plans on giving Deramaxx or a similar NSAID to your dog if he has a cruciate or other ligamentous injury.