An NSAID, or nonsteroidal anti-inflammatory drug, is a medication that relieves pain, fever, and inflammation.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are used for treating your pet's arthritis, inflammation in the eye (anterior uveitis), knee ligament injury (cruciate disease), hip and elbow dysplasia, knee cap dislocation (patellar dislocation), rheumatoid or septic arthritis, abnormal joint cartilage development (osteochondritis dissecans or OCD), spinal arthritis (spondylosis deformans), and cancer pain.
Nonsteroidal anti-inflammatory drugs work by blocking production of prostaglandin molecules that promote pain. NSAIDs revive the spirits of pets by resolving pain, allowing them to exercise so that the heart, lungs, and gut all function normally. With exercise, pets maintain their muscles, and this helps them hold their joints in correct alignment, another reason they experience less pain.
All the cells in the body are surrounded by membranes. One of the molecules found in cell membranes is arachadonic acid. Arachadonic acid can be modified to produce several different types of prostaglandins (PG) molecules, according to what the body needs. Prostaglandin molecules tend to have two functions: they either promote inflammation or promote normal cell function. The type of PG produced is determined by which enzyme modifies arachadonic acid. If the enzyme cyclooxygenase 1 (COX 1) transforms arachadonic acid, PG E1 prostaglandin is produced. If the enzyme cyclooxygenase 2 (COX 2) transforms arachadonic acid, PG E2 prostaglandin is produced.
Generally, prostaglandins of the E1 series work to promote normal function, including normal function of the stomach, liver, heart, and kidney. For example, in the stomach PG E1 helps maintain the mucus lining that protects the stomach from hydrochloric acid. In contrast, prostaglandins of the E2 series work to promote inflammation. Inflammation can be good when the body needs to attack diseases, such as cancer, feline leukemia, or canine parvo. But inflammation can also be bad—for example, when it causes the body to attack itself, as with an immune-mediated disease such as pemphigus, some thyroid diseases, rheumatoid arthritis, and lupus. Inflammation is also bad when it occurs to excess, and immune cells attack like a swarm of bees. This type of excessive inflammation can occur with wear-and-tear osteoarthritis, and with elbow or hip dysplasia.
Understanding prostaglandins and the COX enzymes that produce them allows us to understand how NSAIDs work. NSAIDs either target COX 1 enzymes and the PG they produce, COX 2 enzymes and the PG they produce, or both COX 1 and COX 2.
NSAIDs are medications designed to target the COX enzymes that produce prostaglandins. Some of the newer NSAIDs are somewhat selective (Deramaxx) and target COX 2 more than COX 1. An NSAID that targets COX 2 helps stop inflammation.
The older NSAIDs such as aspirin and Rimadyl (Rx) are less selective, targeting both COX 1 and COX 2, so they decrease beneficial stomach mucus at the same time that they decrease inflammation.
In actuality, no NSAID is completely selective for COX 1 or COX 2. This may be good because the latest research suggests the best pain relief may come from products that affect both COX 1 and COX 2.
About 1% of pets taking NSAIDs have a problem or side effect because of the drug. A common NSAID side effect is gastric ulcer. Your pet may refuse to eat, vomit, and pass dark, tarry stool. Another side effect is kidney damage, causing your pet to drink more and urinate more, a condition called PUPD, or polydipsia, polyuria. Pets may become anemic with pale gums, or they may have yellow (icteric) gums. It is also common for NSAIDs to damage the liver. Fortunately, for most pets the organs return to normal when the NSAID is withdrawn.
In humans, some COX 2 inhibitors affected prostaglandins that protected the heart so that some people taking these drugs suffered heart attacks. Pets don't have the same predisposition to heart attack as humans do, but research has not clarified the full effect COX 2-inhibiting NSAIDs will have on pet hearts.
Medications for people, including NSAIDs, don't necessarily act the same in pets as they do in people. It is never wise to use them without specific veterinary instruction.
Medications for people, including aspirin, don't necessarily act the same in pets as they do in people. Humans often take enteric-coated aspirin, but it is unwise to use these tablets in pets. Enteric coating prevents aspirin from dissolving easily so that it can sit in the pet's stomach for a long time. It's possible for aspirin to "collect" in the stomach, exposing the pet to a toxic dose. It's better to use aspirin, like Excel Aspirin, specifically developed for dogs, or to use a powdery, uncoated aspirin that dissolves easily. It's never wise to use aspirin without specific veterinary instruction.
For cats, aspirin is usually not a wise choice because they metabolize it so slowly it can only be given twice a week. This isn't sufficient to help them with pain. Your veterinarian can recommend more effective analgesics.
Rimadyl has caused liver problems in some dogs—usually Labrador retrievers. They become lethargic, don't eat, vomit, and develop diarrhea. These side effects occur to about 1 in 5000 dogs receiving Rimadyl.
Veterinarians diagnose the liver toxicity with blood tests, and they find that the majority of these dogs make a full recovery after stopping the medication. Some dogs, however, can die or need to be euthanized because of liver damage.
A new use for the NSAID piroxicam is treating cancer of the mouth (squamous cell carcinoma) and of the bladder (transitional cell carcinoma).
As with most things in nature, any medicine that can do so much good, has the potential to do harm. To prevent harm, most NSAIDs require a veterinarian's prescription. Some NSAID side effects warrant your veterinarian requesting blood tests to confirm that the NSAIDs have not damaged the stomach, liver, or kidneys. Some NSAID side effects warrant your veterinarian requesting blood tests to confirm that the NSAIDs have not damaged the stomach, liver, or kidneys.
To prevent the need of NSAIDS for arthritis pain, keep your pet's weight down and start him or her on joint supplements when he or she is young. We recommend Super Joint Enhancer (for dogs), and Phycox with glucosamine. In addition, some veterinarians recommend using Omega 3 fatty acids, such as those found in Super Pure Omega 3, Nordic Naturals Omega-3 Pet (for dogs) and Brite Coat Chews to protect the kidneys, and using Denosyl to protect the liver.