Arthritis in dogs: pharmacological treatment of osteoarthritis
Degenerative joint disease (DJD) or osteoarthritis (OA) is one of the most common causes of arthritis in dogs.
Introduction
OA is a painful, chronic disease of a degenerative and inflammatory nature and multifactorial aetiology that affects different components of the synovial joints.1,2
It is very common in dogs, with an estimated 20% of the population of dogs > 1 year and 90% > 5 years believed to suffer from varying degrees of arthritis.2,3 OA is currently considered an incurable disease in dogs;4 so owners need to accept that treatment is intended to improve the animal’s quality of life and will be for life.2
One of the most important aims of OA management is pain control, which in osteoarthritis is a consequence of the interaction between central and peripheral mechanisms and as such patients can have varying degrees of nociceptive, inflammatory and neuropathic pain.1 Therefore, one would expect multimodal therapy to provide the best results.
Treatment of arthritis in dogs with degenerative joint disease
NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDs)
NSAIDs have been the first-line treatment for arthritis in dogs for many years and their effectiveness is well documented.
- NSAIDs Conventional NSAIDs (carprofen, cimicoxib, enflicoxib, firocoxib, mavacoxib, meloxicam and robenacoxib) produce their analgesic effect through varying degrees of selective action on the cyclooxygenase (COX) isoenzymes. There are no objective data demonstrating a greater efficacy or lower frequency of side effects amongs these drugs.1
- “Priprants”, represented in veterinary medicine by grapiprant are a new class of NSAIDs whose action is due to the antagonistic effect on the EP4 receptors of prostaglandin E2. In theory, this should reduce the side effects associated with COX inhibition. It remains to be clearly established as to whether or not grapiprant is more effective than other NSAIDs in controlling pain in OA.1
ALTERNATIVE TREATMENTS
- Although its use as monotherapy is no longer recommended, paracetamol was used in the treatment of OA in humans. In the UK, a paracetamol/codeine product is authorised for pain control in dogs following trauma and can be administered for up to 5 days. It is not known whether codeine increases the analgesic efficacy of paracetamol in dogs. Nor is there a great deal of evidence about the use of other opiates in dogs with arthritis.1
- Bedinvetmab is a recently marketed canine monoclonal antibody whose analgesic efficacy derives from its ability to bind to the nerve growth factor, which plays a key role in pain generation in DJD.5 In humans, however, a rapid progression of osteoarthritis has been reported if bedinvetmab is used in conjunction with NSAIDs. Although these effects have not been described in veterinary medicine, the combined use of these drugs is not recommended at this time.1
- Given their anti-inflammatory effect, glucocorticoids could occupy a certain role in the treatment of arthritis in dogs, plus their intra-articular administration route is an extra advantage. However, their contraindications and long-term side effects mean their use is still questioned.1
- Based on their effects on neuropathic pain, gabapentinoids (gabapentin or pregabalin) and N-methyl-D-aspartate receptor antagonists (amantadine and memantine) may help control the pain caused by arthritis in dogs. In any case, the available evidence is still limited.1
- The use of cannabinoids as analgesics in patients with chronic pain has become popular in recent years. The results of studies conducted to date in dogs with OA have not been entirely consistent. While some have reported a reduction in the clinical signs, others did not find their use effective.1,6
- For some time now, several substances with a chondroprotective effect have been used in the management of dogs with OA (pentosan polysulphate, chondroitin sulphate, glucosamine and hyaluronic acid, among others), with the idea that they could delay its progression or repair joint injuries. While there are no still data from in vivo studies to confirm this concept, there are indications that some of these products may be clinically effective in the management of OA, although the evidence is not as robust as one would like.1,2
- Other potentially beneficial treatment options, but which require further, correctly designed studies involving large patient groups, include platelet-rich plasma and mesenchymal stem cell therapies.1,7
Conclusions
Arthritis in dogs is a disease that veterinary practitioners have to treat on a regular basis. It is important to explain to owners that the condition cannot be cured, rather the aim of treatment is to offer an adequate quality of life for as long as possible. The selection of the treatment regimen, which is likely to combine more than one product, will depend on the efficacy of each drug in that particular patient and the owner’s cooperation. There is no point in knowing that a drug is effective if it cannot be administered correctly. The combination of components in a special diet, such as the ADVANCE ARTICULAR diet, is an option to consider to help ensure a daily intake of micronutrients that act to improve bone, cartilaginous tissue and joint fluid.
