What is an NSAID?
NSAID (pronounced “en-sed”) stands for “nonsteroidal anti-inflammatory drug”. Because NSAIDs have an anti-inflammatory effect, they are most often used to reduce pain and inflammation. They may also be used to reduce fever. In pets, they are most commonly used around surgical procedures, after injury, or to help manage chronic pain such as that of osteoarthritis. This is similar to how ibuprofen and naproxen are used by humans.
Common NSAIDs prescribed in veterinary medicine include carprofen (Rimadyl®), meloxicam (Metacam®), deracoxib (Deramaxx®), firocoxib (Previcox®), robenacoxib (Onsior®), grapiprant (Galliprant®), and acetylsalicylic acid (Aspirin®).
How do NSAIDs work?
NSAIDs primarily interfere with only one of the main pathways of inflammation, in contrast to steroids, which inhibit many pathways of inflammation.
When a cell in the body experiences trauma or is damaged, a chain reaction of events is set in motion. Think of the many things that happen if you stub your toe: you immediately jerk your foot back or up; you may reach for it in a reactive motion; your toe hurts, may turn red, or feel numb, swollen, or throbbing; later, you may notice bruising. All of those reactions and sensations were part of a chain reaction from one injury.
That injury (and most cellular damage) initiates the cyclooxygenase (COX) pathway of inflammation. This pathway starts with the activation of a protein (COX) and leads to the sensation of pain.
NSAIDs work by interfering with the COX pathway, either by blocking COX itself or by blocking the activity of other chemicals further down the COX pathway. By blocking this pathway, pain can be significantly reduced.
An activated COX pathway leads to pain and inflammation; however, COX isn’t all bad. COX helps the body in many ways, by protecting the lining of the stomach and intestines, maintaining adequate blood supply to the kidneys, and supporting platelet function for normal blood clotting (hemostasis), among other functions.
Can NSAIDs cause harm?
The COX pathway can have a protective effect on bodily functions, so there is potential for NSAIDs to have adverse effects when the “good” COX pathways are blocked, in addition to the pain-related COX pathways.
Gastrointestinal
NSAIDs can affect the gastrointestinal tract, causing symptoms such as vomiting, reduced or no appetite, changes in stool (e.g., dark coloration or diarrhea), lethargy, or abdominal pain.
NSAIDs can cause gastrointestinal changes both directly and indirectly. Directly, NSAIDs can cause local irritation to the stomach lining, especially if given on an empty stomach. Indirectly, NSAIDs can reduce the protective mucus layer of the stomach lining and intestines, leaving these organs more vulnerable to the acidic environment and digestive enzymes, and potentially causing gastrointestinal ulcers. COX is needed to heal ulcers, so NSAID interference with the COX pathway may delay or prevent healing of existing ulcers.
Kidneys
NSAIDs can also affect the kidneys. Parts of the COX pathway act as a protective mechanism to support kidney health during times of kidney stress, such as when a pet is dehydrated, has low blood pressure (hypotension), or has elevated sodium levels. NSAIDs given to a pet with one of these conditions can result in kidney injury and reduced kidney function, or in the worst cases, acute kidney failure. Signs of kidney injury include reduced appetite, vomiting, diarrhea, lethargy, increased thirst, increased or decreased urination, stumbling, or weakness.
Liver
NSAIDs very rarely cause liver damage (acute hepatic necrosis). Such damage is mostly seen in Labradors and similar breeds. This is known as an idiosyncratic reaction and is believed to be immune-mediated (an abnormal and unexpected reaction of the immune system that causes damage in the body).
Signs of liver problems with NSAIDs may be subtle and only recognizable through blood tests, or they may be like those seen with gastrointestinal ulceration: vomiting, diarrhea, poor appetite, lethargy, and abdominal pain. A dog with severe liver disease may also be jaundiced, showing yellowing of the gums, skin, and the whites of the eyes.
Blood Clotting
Some NSAIDs, like aspirin, can affect the body’s ability to clot, resulting in uncontrolled hemorrhage that may look like bruises in the skin or gums.
Most adverse effects of NSAIDs are mild but shouldn’t be ignored, as they can become worse, especially if the medication is continued or used inappropriately. Severe adverse effects include gastrointestinal perforations (holes in the gastrointestinal tract that allow the contents to spill into the abdomen), kidney failure, and liver necrosis. These adverse effects are more rare but can lead to death in some cases.
If NSAIDs can be harmful, why does my vet recommend them?
In most cases, the benefit your pet gets from NSAIDs outweighs the risk of adverse effects. NSAIDs are one of the most effective treatments for inflammatory pain such as that experienced with surgery, injury, or osteoarthritis. The gradually increasing chronic pain of osteoarthritis can be debilitating, affect mental health, nutrition, and quality of life. Using NSAIDs chronically in pets with osteoarthritis can greatly reduce pain, increase their mobility, and overall improve their quality of life.
Several consensus groups describe NSAIDs as important treatments for chronic or osteoarthritic pain, including the World Small Animal Veterinary Association (WSAVA), the American Animal Hospital Association (AAHA), and in the Canadian Osteoarthritis Treatment Summary Guide. Your veterinarian will prescribe them if they feel that using them is in your pet’s best interest. Talk to your veterinarian if you have any concerns.
Is there a way to reduce the chance of adverse effects?
Adverse effects can’t be avoided 100% of the time. Before starting an NSAID, your vet may recommend screening your pet for any easily detectable diseases that could predispose them to an adverse effect, such as liver or kidney disease. This screen often includes blood tests such as a complete blood count (CBC), a biochemistry profile, and a urinalysis. Your veterinarian may recommend repeating this testing within a few weeks of starting an NSAID to see if there are any hidden effects of the drug on your pet.
With chronic NSAID use, repeated testing, as well as a physical exam, is often recommended at least every six months to detect any changes in the early stages, before your pet shows symptoms.
For osteoarthritis, NSAIDs are often recommended at the lowest effective dose, meaning the lowest possible dose that still adequately controls the pain of your pet’s condition. You may be able to decrease the need for high doses of NSAIDs by using many ways to manage chronic pain. See the handout “Multi-Modal Pain Management in Dogs” or speak with your veterinarian for more information.
An NSAID should never be combined with another NSAID or a steroid medication, as this greatly increases the risk of a serious adverse event.
Remember to let your veterinarian know all medications, supplements, creams/ointments, and food your dog receives and discuss any new supplements or medications prior to starting them. Some supplements like devil’s claw, or creams containing steroids or other NSAIDs, may increase the risk of adverse events when given with an NSAID.
You must also notify your veterinarian immediately if you see any changes in your pet. It may be best to discontinue the NSAID until the cause is identified.
Is one NSAID better than another?
Aspirin has a higher risk of GI ulceration than veterinary NSAIDs, because it interferes with more aspects of the COX pathway than newer NSAIDs.
Of the many newer NSAIDs developed over the past 20 years, none have shown to be better than another or have a higher risk of adverse events versus the others. We know that individual pets respond better to some NSAIDs than others though, so your veterinarian may recommend trying a different NSAID if your pet doesn’t respond well to the first one prescribed. Your pet will need to go through a “washout” period, allowing time for the first NSAID to completely be excreted from their body before starting another NSAID. Your veterinarian will recommend other pain control treatments to use during this time.
Are NSAIDs used for cats?
There is no NSAID approved for long-term use in cats in the United States; however, there are approved NSAIDs in Canada, Europe, and Australia. Several studies have demonstrated safety and effectiveness in cats and NSAIDs are often recommended by veterinary pain management specialists. Your veterinarian will discuss if NSAIDs are the right treatment for your cat. It’s important to never use medication prescribed for a dog in your cat without speaking to your veterinarian, as some medications that are safe for dogs can have serious side effects in cats.
What is the takeaway message when it comes to NSAIDs?
NSAIDs have the potential to cause harm; however, they are regularly used in veterinary medicine because of their ability to treat pain and improve quality of life for many pets experiencing chronic pain. In most cases, the benefits outweigh the risks, and you can minimize adverse effects by discussing the treatment with your pet’s veterinary care team, knowing what to watch for, and ensuring your pet gets regular checkups and monitoring.
