Arthritis in Dogs
|THE PET PHARMACY|
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Arthritis: Medications for Degenerative Arthritis
Our newest drug is Galliprant
Galliprant®(grapiprant tablets) is a new class of anti-inflammatory that targets pain, so you can start targeted pain relief from the earliest diagnosed stages of canine OA. Give these dogs the relief they need and help keep them doing the things they love.
- Galliprant is a first-in-class piprant; a non-COX-inhibiting prostaglandin receptor antagonist (PRA)
- Galliprant does not inhibit the production of many housekeeping prostanoids that maintain homeostatic functions
- It specifically blocks the EP4 receptor, the primary mediator of canine OA pain and inflammation
Degenerative joint disease is the number one cause of chronic pain in dogs and cats. The condition is the result of long-term stresses on a joint, either resulting from an old injury or from natural development of a poorly conformed joint. While surgery may be able to help in some situations, most of the time the degeneration of the joint cannot be reversed and treatment focuses on preventing progression of damage. Numerous products are available; some are best combined with others and some cannot be combined. What we do know is that arthritis pain is best addressed by what is called a multi-modal approach, meaning that several approaches combined yield better results than any single therapy. Here, we focus on medications.
Medications for arthritis pain are divided into two groups: Slow-acting drugs and fast-acting (non-steroidal anti-inflammatory drugs and cortisone-type drugs).
Slow-acting drugs for arthritis ultimately improve joint function and help with pain relief, but they require a time frame of weeks to months to exert their effect. They may have disease-modifying properties such that their benefit continues even after their use has been curtailed. These products are typically what are called neutraceuticals, meaning that they are nutritional supplements that have medicinal properties. Most arthritis patients can benefit from their use and they are considered a basic starting level for joint care.
- Because the FDA classifies these as neutraceuticals, (i.e. nutrients with medicinal properties) rather than as drugs, the usual rigorous testing for efficacy has not been required. As a result, the optimal dosage has not been determined and almost every product has a different dose recommendation. Some experimentation may be necessary.
- These products are not likely to be helpful for spinal arthritis as the joint composition of an intervertebral disc (the joint of the spine) is totally different from those of other bones.
- These products can be used in both dogs and cats.
- These products often complement treatment with anti-inflammatory medications.
Glucosamine and Chondroitin Sulfate
These products are cartilage components harvested chiefly from sea mollusks (i.e., cartilage is made up of chondroitin sulfate and glucosamine metabolites, among other things). By taking these components orally (pills in the mouth), the patient is able to have plenty of the necessary building blocks needed to repair damaged cartilage. It is also felt that these products may have some anti-inflammatory properties separate from their structural uses. Unlike the anti-inflammatory medications described later on, these products do not produce rapid results; one to two months are needed for them to build up to adequate amounts. There are numerous products available combining glucosamine, chondroitin sulfate, assorted vitamins, creatine (a muscle building block), omega 3 fatty acids and more. Many senior or joint supporting diets are well fortified with glucosamine.
Omega Three Fatty Acids
Certain dietary fats, typically cold water fish oils, have been found to have anti-inflammatory properties. While this finding has primarily been used in the treatment of itchy skin, many arthritic dogs and cats have also benefited from supplementation. While there are no toxic issues to be concerned with, these products require at least one month to build up to adequate amounts. Effects are not usually dramatic but can be helpful.
It should be noted that the flax seed oil is readily converted to omega three fatty acids in the human body. This conversion is not so easy in the canine or feline body; only about 10% of the oil is converted. It is a waste to add flax seed oil to pet food; fish oils are needed. Numerous brands are available and chances are your veterinarian stocks one. The appropriate dose is still somewhat controversial but the ratio of EPA (eicosapentenoic acid) to DHA (docosahexenoic acid) should be 3:2.
MSM stands for methyl sulfonyl methane and represents another nutraceutical anti-inflammatory agent. MSM is in most plant and animal tissues and is a natural source of sulfur; however, for commercial sale MSM is derived from DMSO (dimethyl sulfoxide), a solvent that comes in both medical grade and industrial grade. One might wonder why a sulfur source would be helpful in treating arthritis. The glycosaminoglycans that enable cartilage to soak up water and thus act as a cushion for articulating bones are all sulfates. The idea is to provide nutritional building blocks for cartilage repair. Beyond this, MSM seems to have anti-inflammatory properties and may act as an anti-oxidant (see below).
Anti-oxidants and Free Radical Scavengers
Free radicals are harmful biochemicals that can attack us from external sources (such as pollution, sunlight, etc.) or we make them ourselves as by-products of oxygen use. These harmful little molecules are highly reactive and attack our structural proteins as well as cause production of assorted inflammatory proteins. One prominent theory of aging centers on free radicals with the idea that the damage free radicals cause to our brains, skin, joints etc. is the foundation of age-related debilitation. Normally, our bodies use natural anti-oxidants to inactivate free radicals; in this theory, supplementing with additional anti-oxidants can retard age-related change.
Anti-oxidants that are readily available include Vitamin C, Vitamin E, SAMe, Superoxide Dismutase (S.O.D.) and others. Oxtrin® and Comfort Tabs ® (S.O.D.) are marketed for joint support. Denosyl (SAMe) is marketed for animals primarily for its effects in the liver, though in humans its joint-related results are a primary focus.
Non-Steroidal Anti-Inflammatory Drugs
Most pets with arthritis pain need relief now, not in 1 to 2 months when the cartilage building blocks and nutritional anti-inflammatories have had a chance to build up. The next mode of therapy is the NSAIDs, or non-steroidal anti-inflammatory drugs.
These medications act quickly by suppressing the inflammatory biochemicals that ultimately lead not only to the pain of arthritis but also to cartilage damage. None of these medications can safely be combined with one another. Furthermore, human NSAIDs tend to be toxic to pets, especially cats. While aspirin has some potential use in relieving joint pain, safer medications developed specifically for pet use have become the standard for joint pain management. Never use a human medication of any kind in a pet without specific instructions on how to do so from your veterinarian.
The following NSAIDs are available for pets:
Carprofen (Rimadyl®, Vetprofen®)
Galliprant is our newest NSAID in 2017. It selectively treats inflammation due to arthritis without the side effects that may be seen with the older NSAID drugs. It does not affect the "good" prostaglandins that protect kidneys and intestinal function.
These medications work by distinguishing between two prostaglandin producing enzymes: cyclooxygenase I and cyclooxygenase II. Older drugs, such as aspirin, inhibited both forms of cyclooxygenase alike, which meant that they curtailed production of both inflammatory prostaglandins as well as the “good” prostaglandins that help promote kidney circulation and intestinal health. Developing drugs that can distinguish between these enzymes has made it possible to develop safe anti-inflammatories for pets. Still, it is important to realize that classifying prostaglandins as “good” and “bad” is an oversimplification. Pre-treatment screening blood tests are still important before using an NSAID as a pre-existing kidney or liver condition may preclude their use. Monitoring tests typically are recommended every six months for pets on NSAIDs.
If a pet has or comes to develop a condition that is not compatible with NSAID use, one of the analgesics listed below would be a fair alternative.
(general cat graphic on the left)
It is important to mention that cats are uniquely sensitive to all NSAIDs and it is tricky to find one that is appropriate. Of the list presented here, only meloxicam is appropriate for long-term feline use and only with some dose modification.
Analgesics that are not Anti-Inflammatory
Sometimes the combination of a cartilage-protecting agent and an anti-inflammatory drug is not adequate for pain control. There are several appropriate pain relievers that can be used in pets. These medications are strictly analgesics and do not modify the inflammation in the joint.
- Tramadol is a narcotic pain reliever similar in many ways to codeine. The pill size makes it a bit tricky for feline use.
- Amantadine is an antiviral medication found to relieve chronic pain.
- Gabapentin, originally an anti-seizure drug, has been found to have effects on chronic pain especially pain from pinched or inflamed nerves.
The medications can be used in cats and dogs alike and are compatible with all other the other medications listed. A synergism occurs when these medications are combined with NSAIDs such that the combination of both drugs produces greater results than one would expect.
This treatment does not fit readily into the classification system proposed above. Adequan is an injectable cartilage component called polysulfated glycosaminoglycan (mostly chondroitin sulfate), but instead of coming from sea mollusks, Adequan is derived from the windpipe cartilage of cattle. Adequan has numerous beneficial effects for the arthritis patient including the inhibition of harmful enzymes involving joint cartilage destruction, stimulation of cartilage repair, and increasing joint lubrication. These effects go far beyond simply providing plenty of chondroitin sulfate as a building block for damaged cartilage.
- Adequan is given as an injection and so is able to reach all joints but it seems to have a special affinity for damaged joints.
- Adequan should be avoided in patients with blood clotting abnormalities as a matter of caution. (At excessive doses tested in normal patients, abnormal clotting resulted so it is best not to take a chance in an abnormal patient.)
- Adequan is best given as a series of injections, twice a week or so until a response is seen but not exceeding eight injections. After an effect is seen, Adequan injections are given on an as needed basis.
- Adequan is formally approved for use in dogs and horses but may also be used in cats with good results.
- Adequan may be combined with any of the other medications listed on this page.
In conclusion, the arthritic pet has a large menu of medications to select from and while proper medication is an important part of therapy, weight control and proper exercise should not be forgotten. Proper exercise is excellent physical therapy for the arthritic pet, as it is crucial to maintain as much muscle mass as possible to support the abnormal joint. Massage and gentle flexion/extension of the joint may also help. Remember, treatment for joint disease is likely to involve a combination of medications in addition to physical activity.