Brenda G. Mills, DVM
Arthritis is a condition affecting the joints. It can affect any moving joint in the body, including the joints of the legs, paws, spine
and jaw. Arthritis occurs when the shape of the joint is imperfect, either because of a genetic conformation defect (i.e. hip
dysplasia), injury to the joint or to the structures stabilizing a joint (a fracture or a ligament injury), or normal wear and tear (old
age). Imperfections in the surfaces of a joint increase friction, and arthritis is the joints’ way of attempting to increase stability.
Parts of a Joint:
All joints where movement occurs contain the following structures:
Articular surface: This is the bony surface involved in the joint, where movement occurs. There are two or more of these in
each moveable joint.
Cartilage: A cushiony, resilient, rubbery tissue that covers articular surfaces. Cartilage decreases friction and absorbs and
distributes the shock of impact in the joint.
Joint fluid: A thick fluid which, similar to oil in a car engine, lubricates the joint. The fluid also helps distribute and absorb the
shock of impact.
Joint capsule: A fibrous tissue that surrounds the joint. The capsule keeps the joint fluid within the joint space. Special cells in
the joint capsule are responsible for producing and maintaining the joint fluid.
Tendons: Tendons attach muscle to bone, permitting muscle to act on a joint to create movement.
Ligaments: Ligaments attach bone to bone. They are tough, fibrous bands that help hold the bones of a joint together, keep joints
stable, and help keep them from bending “in the wrong direction.”
Friction and Inflammation
Damage to any of these components will affect the overall structure of a joint by creating friction or instability. The bones
involved in a joint will modify in response to instability in an attempt to restore normal function. Unfortunately, bone is not a
very intelligent tissue, and these structural changes usually create more friction within the joint rather than less. The increased
friction wears thin spots or holes in the cartilage, causing the bone to attempt to adapt further, resulting in more friction. . .
Inflammation then follows, which causes the joint fluid to become thinner, making it a less effective lubricant, increasing friction
and causing the joint to be painful. Treating arthritis, then, focuses on decreasing inflammation, usually with non-steroidal anti-
inflammatory drugs (NSAIDs), and preserving or improving joint fluid quality (often with glucosamine, chondroitin, or other
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
NSAIDs are drugs that inhibit inflammation by affecting the function of an enzyme in the “inflammatory cascade” (a series of
chemical reactions that results in inflammation). There are two forms of the enzyme that NSAIDs can interfere with,
cyclooxygenase 1 and cyclooxygenase 2 (COX1 and COX2). COX1 is present in many tissues and participates in normal
function, while COX2 is almost exclusively involved in inflammation. Certain NSAIDs affect one form of the enzyme more than
the other. It is preferable to use NSAIDs that are COX2 specific because they are less likely to cause side effects like stomach
ulcers than drugs that affect COX1. NSAIDs that are COX2 specific in one species may be less COX2 specific in others,
meaning that drugs that appear to be highly effective in humans may be less effective in dogs, and vice versa.
Aspirin is the NSAID most commonly used by the general public. Aspirin is not COX2 specific, meaning that there is a
significant potential for the development of adverse reactions such as gastrointestinal ulceration. The effectiveness of aspirin
varies greatly based on the preparation and manufacturer. The dose that is generally required for control of arthritic pain in dogs
was shown to cause stomach or intestinal ulcers in 50% of the dogs in one study. We do not recommend aspirin for the pain
control on a day to day basis.
Carprofen was the first prescription NSAID approved for use in dogs in the United States. Carprofen is more potent than
aspirin, and appears to be relatively COX2 specific. Carprofen has a very low incidence of causing intestinal or stomach
ulcers. There is a low risk (0.02%) of developing liver disease while on Carprofen, and a lower risk of injury to the kidneys.
In almost all cases, stopping the drug and administering supportive care leads to complete recovery.
We prescribe carprofen for arthritic pain and for pain associated with trauma. Carprofen is given twice daily.
Etodolac appears to be relatively non-COX-specific in the dog. It has a higher risk of causing ulcers, but a lower risk of liver or
kidney problems than Carprofen. The risk of developing stomach or intestinal ulcers appears to be dose-dependent, meaning
that the risk is increased with higher doses (i.e. greater than the prescribed dose).
EtoGesic is given once daily. We prescribe it for long-term control of arthritic pain or for pain associated with injury or
trauma. In some patients, EtoGesic appears to work better than Rimadyl.
Deracoxib is a coxib class NSAID, similar to Celebrex. The coxibs almost exclusively affect the COX2 enzymes, significantly
reducing the incidence of adverse effects and increasing the effectiveness of the drug. At high doses, Deramaxx may cause
kidney parameters to become elevated, but safety studies showed no adverse effects on monitoring blood work performed on
dogs given the label dose. Deramaxx is has been associated with severe adverse reactions and even death when given long-term
at doses greater than the label dose or when given in conjunction with steroids or other NSAIDs.
Deramaxx is given once daily and is used for chronic arthritic pain as well as for post-operative pain at a higher (short-term)
dose. Deramaxx has shown to be significantly more effective for pain control than Rimadyl in many dogs.
Metacam is an oxicam-class NSAID which has been used successfully in humans. Metacam was approved for use in dogs in
Europe several years before receiving approval in the United States, and is approved for use in cats. Metacam is delivered as a
liquid which most dogs seem to find palatable, dosed at “one drop” per pound of body weight or per a specially labeled
syringe. Metacam has proven to have a very low incidence of gastrointestinal effects, but is known to cause kidney failure with
Metacam is given once daily to dogs for chronic arthritic pain and sometimes for post-operative pain after giving a dose of the
injectable product first. Metacam is given once every three days to cats for the control of post-operative pain or for chronic
Previcox is the newest of the coxib-class NSAIDs to be approved for use in dogs. It is the first NSAID ever to be developed
specifically for dogs – previously, all NSAIDs approved for dogs have been drugs that have been developed for human use (and
in some cases failed the protocols for human use). Based upon the safety tests, Previcox appears to be the NSAID least likely to
cause gastrointestinal ulceration or adverse reactions in any organ. Previcox is also the only NSAID to have been tested in
puppies, which experience the greatest risk of adverse reactions with any NSAID. In clinical trials, Previcox compared
favorably to Rimadyl and Etogesic for pain control, and Previcox has in our experience proven to provide pain control superior
to that of any other NSAID.
Previcox is given as a once daily chewable tablet for the control of pain due to acute injury, chronic inflammation, or post-
Phenylbutazone (“Bute”) was one of the earliest prescription NSAIDs available for veterinary use. Phenylbutazone causes
bleeding disorders, liver disease, and kidney problems at a much higher rate than newer prescription NSAIDs. Phenylbutazone
has also been shown to cause cartilage to break down. We do not recommend phenylbutazone for use in small animals.
Over-the-counter NSAIDs should be used with extreme caution in pets. Naproxen (Anaprox) and Ibuprofen (Advil, Midol)
cause severe intestinal ulcers at low does in dogs. Acetaminophen (Tylenol) can cause severe illness at high doses. Please call
our office to check safety and dosages prior to giving your pet any over-the-counter drug. These drugs are not recommended for
“Chondroprotective” is the term used to describe any drug acting to inhibit damage to or promote the regeneration of cartilage.
These drugs are useful in the long-term treatment of arthritis, slowing the progression of arthritis, decreasing pain, and frequently
decrease the need for NSAIDs. Chondroprotective drugs are also beneficial in athletic and long-backed animals, helping reduce
the risk of developing arthritis due to day-to-day trauma. We currently recommend the use of chondroprotective supplements
such as glucosamine in all pets, regardless of their age, as a preventive measure.
Adequan is an injectable drug which has been shown to inhibit the degradation of cartilage by improving the viscosity of joint
fluid (making the fluid thicker), mimicking the glycosaminoglycan that occurs naturally in joint fluid. Adequan also promotes
cartilage repair, though how it does this is not known. The only adverse effects seen with Adequan use is prolonged bleeding
times (at high doses) and occasional pain and swelling at the site of injection. Adequan is given twice weekly for four weeks,
followed by oral chondroprotective drugs.
Glucosamine is a precursor to the molecule in joint fluid that Adequan mimics. Studies in humans and animals have indicated a
significant improvement in mobility, decrease in pain, and inhibition of the progression of arthritis with the use of glucosamine.
Glucosamine use can significantly decrease the need for NSAIDs. Glucosamine is available in both human and veterinary
formulations. There is a difference between glucosamines. Glucosamine HCl is the best absorbed, followed by glucosamine
sulfate. Other chemical forms of the molecule are so poorly absorbed as to be virtually useless. Consumerlabs.com tested 20
different glucosamine products sold for human use, and found that only one brand, Cosamin by Nutramax Labs, actually
contained the amount and form of glucosamine stated on the label. Purchasing a less expensive formulation of glucosamine will
not necessarily be cost effective. Ask your veterinarian about the preferred products at this time.
Chondroitin is an important part of the fibrous component of cartilage and also inhibits the activity of enzymes that degrade joint
fluid. The concentration of chondroitin in joint fluid decreases with age, which may contribute to the formation of arthritis in
older animals that had good joint conformation as youngsters. Chondroitin in a purified form is well-absorbed; chondroitin
present in shark cartilage and other “natural” preparations is less readily available to the body. Chondroitin is available as a
human preparation or in veterinary supplements. Many of these supplements contain glucosamine as well. Chondroitin with
glucosamine is generally regarded as more effective than either alone.
Superoxide Dismutase (SOD)
Superoxide Dismutase is an enzyme that occurs naturally in many tissues. This enzyme acts as a “free radical scavenger”
(antioxidant) – it binds byproducts of inflammation that may be toxic to tissues. Superoxide dismutase may help reduce the need
for other anti-inflammatory medication, and has a very wide margin of safety with very low risk.
Antioxidant vitamins (A, C, E)
The antioxidant vitamins act as free radical scavengers, similar to superoxide dismutase. While their action is less potent and
less specific than that of superoxide dismutase, they may help mitigate damage secondary to chronic inflammation. Care should
be taken, though – studies have shown that giving dogs high doses of vitamin C and then withdrawing the vitamin suddenly may
cause symptoms of scurvy.
Chiropractic care may not inhibit the progression of existing arthritis, but can help optimize the function of arthritic joints.
Chiropractic adjustments can also help your pet compensate for achy joints by assisting the body in correcting trauma caused to
other joints by the abnormal stresses created when an animal shifts weight off of a sore limb. Chiropractic adjustments can also
help delay the onset of arthritis due to chronic injury by restoring joint motion after injury and assisting the body in healing mild
Acupuncture is an ancient method of disease treatment dating back at least 2000 years. The insertion of needles into acupuncture
points is believed to stimulate nerves, modifying the conduction of sensory input such as pain and possibly initiating a feedback
loop that can result in the reduction of inflammation. Acupuncture is currently recommended by many pain control specialists
working in human medicine.
THE BOTTOM LINE
Arthritis is an age-associated disease, and is responsible for most of the “slowing down” that we recognize in older pets. The
severity of the pain associated with the arthritic changes is very dependent upon the individual – our tolerance to pain, obesity,
how gradually the pain sets in, the joints affected, and our ability to compensate. Depending upon the stage of the arthritic
changes, multiple treatment modalities are available, ranging from dietary supplements and chiropractic care to NSAIDs and
opiods or acupuncture.
To borrow a quote from the Deramaxx ad campaign, “No (pet) should be in pain.”
We recommend that all arthritic patients receive physical examinations once every six months, to monitor overall health status
and the progression of arthritis. Little things like being 10% overweight can have a dramatic negative impact upon the ability of
an arthritic pet to get through the day. For patients on long-term medication, especially NSAIDs, some degree of laboratory
monitoring is recommended every six months as well. Even in the absence of long-term medication, blood work is advisable to
monitor thyroid level, urinary health, and other factors that can adversely affect your pet’s well-being.
We do recommend running screening blood work prior to giving any NSAID long term, and every 6 months while the patient is
on the drug. Even the safest, most COX2-specific NSAID must be used with caution in animals with kidney, liver, or other
metabolic diseases. Toxicity may occur in sick patients which would not occur in metabolically normal animals. The goal of
performing monitoring blood work is to prevent such toxicities by catching any abnormality while it is still a laboratory value
and before it becomes a problem for the patient
.A serious, potentially life-threatening adverse reaction can happen with the use of any NSAID, even Tylenol in people.
Vomiting, diarrhea, intestinal or stomach ulcers, and circulatory problems are the most common adverse reactions. If your dog
seems to be ill in any way while taking an NSAID, stop giving the drug immediately and call us for an appointment. We will
do a physical exam and check blood work to rule out liver or kidney problems.
Giving two different NSAIDs together can result in rapid onset, severe adverse reactions, including death. If your pet is on an
NSAID, please remember that it may be extremely dangerous to give your pet anything additional for pain or to increase the
dosage of the NSAID you are using. If your pet’s pain becomes too severe to be adequately controlled by the dose of the NSAID
you are using, please contact your veterinarian about switching drugs or adding an opiod such as tramadol or codeine. When
switching NSAIDs, a “drying off” period is typically recommended to make certain that the previous drug is completely out of
the animal’s system prior to starting the new drug, minimizing the potential for adverse reactions. Two weeks is generally
accepted as “safe,” but in many cases it is unacceptable to leave the pet without NSAIDs for two full weeks, and a one week or
shorter period without drugs may be recommended prior to starting the new drug. Steroids should be avoided or used with
extreme caution in animals that are taking any NSAID.
|This client information is written by Dr. Brenda Mills, DVM