MANAGING THE OA-AFFLICTED DOG

Transcription

1 Vet Times The website for the veterinary profession MANAGING THE OA-AFFLICTED DOG Author : Samantha Woods Categories : Vets Date : July 30, 2012 SAMANTHA WOODS discusses treatment of osteoarthritis in dogs, including pain management with NSAIDs and other drugs, exercise and physiotherapy THIS article aims to provide an overview of the medical management of canine osteoarthritis (OA), focusing on effective treatments and the use of NSAIDs. Advances in the treatment of small animal osteoarthritis will be covered in an article to be published later in the year. OA or degenerative joint disease (DJD) is the most common type of arthritis occurring in dogs and cats ( Figure 1 ). In dogs, OA usually develops secondary to an initiating cause, such as joint laxity or instability, osteochondrosis, trauma or ligamentous damage. The disease can be severely debilitating and is characterised by the destruction of articular cartilage, leading to pain and reduced function of the diseased joint, remodelling of bone with subsequent osteophyte formation and intermittent inflammation ( Figure 2 ). While cartilage damage is often considered to be the sole cause of OA it is important to remember it is a disease of the entire joint including the articular (hyaline) cartilage, the synovial membrane and fluid, subchondral bone and the supporting muscles and ligaments within the joints. Management In many cases, signs associated with OA may lead to investigation and treatment of the primary condition for example, cranial cruciate ligament disease, fragmentation of the medial coronoid process and hip laxity. In cases where the primary cause cannot be identified or managed, OA 1 / 6

2 should be treated as a separate disease entity. In end stage disease salvage, surgical procedures may be necessary for example, total hip replacement or joint arthrodesis. However, medical management is appropriate for most cases and a multimodal approach can lead to significant improvement in quality of life for affected patients. Pain management NSAIDs, with their analgesic, anti-inflammatory and antipyretic properties, are the mainstay of treating dogs with OA. They relieve the clinical signs of pain by suppressing prostaglandin (PG) release from the metabolism of arachidonic acid by the enzyme cyclo-oxygenase (COX). The prostaglandin PGE2 plays a number of roles in enhancing the development of OA, including lowering the nociceptive threshold, promoting synovitis, enhanced formation of matrix metalloproteinases that stimulate cartilage degradation, and reducing chondrocyte activity, which reduces cartilage matrix synthesis and repair. PGE2 also lowers the nociceptive threshold in patients with OA. Some prostaglandins have protective effects in the body, which include maintaining gastrointestinal tract health, enhancing platelet aggregation and facilitating renal function. The goal of treatment with NSAIDs is to inhibit the synthesis of prostaglandins that contribute to OA while sparing those involved in normal physiology. Historically, it was understood that beneficial PGs are produced through the COX-1 isoenzyme suggesting that sparing this would be advantageous for normal physiological function. However, this idea is over-simplistic, since COX-2 has now been found constitutively expressed in the kidney and brain and has been shown to have a protective effect on injured gastrointestinal mucosa. The newer coxib class of NSAIDs is more COX-2 selective and COX-1 sparing. These drugs have strong efficacy and good safety profiles, making them a good first-line choice for OA pain treatment. Table 1 shows a number of NSAIDs licensed for use in dogs in the UK. While ketoprofen, phenylbutazone and tolfenamic acid are listed and licensed for treatment of chronic locomotorassociated pain, they are less commonly used in the clinical situation compared to the newer NSAIDs available. It is important to remember every dog responds to medication differently. In one study using objective forceplate assessment of gait, and comparing multiple contemporary NSAIDs in dogs, every dog tested responded to an NSAID, but not every dog responded to each one (Millis, 2006). In a clinical setting, if a dog does not respond to one NSAID, it is worth changing to another. However, a washout period between the two is prudent to minimise side effects. A three to fiveday washout period has been suggested as a sensible precaution in cats when changing from one NSAID to another (Sparkes et al, 2010). As with all drugs, patientdependent intolerance may occur with prolonged NSAID use. Regular assessment of these patients is necessary and dosage alterations made as required. As patients 2 / 6

3 age and develop the potential for subclinical compromise of hepatic and renal function, it is sensible to treat with the minimum effective dose. This will also help to minimise long-term side effects of the drugs. Weight management Obesity is a major risk factor for both the development of OA and the requirement of analgesia to treat OA ( Figure 3 ). Increased bodyweight not only affects pain by increasing the amount of weight being transmitted through a diseased joint, but also through the complex roles of adipose tissue, which is both an endocrine and secre tory organ. Adipocytes secrete a number of proteins or adipokines that act as inflammatory mediators. In obese patients, production of these proteins increases, leading to a continued state of low-grade inflammation and potentially contributing to the pathophysiology of inflammatory diseases, such as OA. In clinical OA cases, weight control is of paramount importance. The loss of between six to eight per cent bodyweight has been shown to significantly improve limb function using objective (force plate) measures in a study (Marshall et al, 2010). Exercise control Osteoarthritic patients need controlled exercise to limit joint stiffness and maintain limb movement while avoiding impact exercises that cause stress on the affected joint. Patients that do not exercise also often gain weight. Lead exercise of increased frequency (three to four times daily), but of reduced duration, perhaps 10 to 15 minutes per exercise period, is often recommended. Many osteoarthritic dogs prefer to exercise on flat, even ground and softer surfaces. Evidence to support these recommendations is, again, scarce, and from a practical point of view, an exercise regime should be tailored to the individual patient and situation. Physiotherapy While studies have shown dogs benefit from a passive range of motion and stretching exercises postoperatively (Salter et al, 1984), few studies have demonstrated their benefit in dogs with OA. Hydrotherapy and swimming are also very popular for the postoperative management of canine patients, but no firm evidence exists to support their use for treating OA in dogs. Swimming encourages a greater range of joint motion; however, there are significant differences in the way limbs and joints function between normal walking and swimming activity in dogs. These abnormal movements can create additional forces on the joints and supporting structures and may lead to further injury and discomfort. Hydrotherapy treadmills allow the joints to function in a more normal fashion, but again the literature lacks firm evidence to support its use in these patients. 3 / 6

4 Nutritional supplementation Nutritional supplements are commonly used to treat dogs with OA, although again, peerreviewed published literature lacks support for their use. The most striking reports of dietary modulation of OA pain are those that contain high levels of omega 3 fatty acid (eicosapentaenoic acid), glucosamine and chondroitin sulphate. These diets have proven efficacy in OA treatment with regard to objective studies of lameness and subjective owner and veterinarian assessments (Roush, 2010). No clinical evidence exists to support the structure-modifying effects of these compounds when used in isolation in dogs. Other analgesic drugs Patients with controlled endstage OA may demonstrate breakthrough periods following increased levels of activity where their usual NSAID analgesia is not effective. In these patients a combination of multimodal analgesia can be used to manage the perceived discomfort. In the short term, paracetamol in combination with codeine is a licensed preparation that can effect significant analgesia. It is advised this should not be used in conjunction with another NSAID. For longer term management, opiate analgesia can be combined with NSAIDs to alleviate OAassociated discomfort. Codeine, tramadol or buprenorphine have been commonly used in association with NSAIDs, although there is no published data relating to their efficacy in clinical OA and their use is off-licence. The efficacy of these agents also differs between individuals. The use of N-methyl-D-aspartate (NMDA) inhibitor amantadine, in combination with an NSAID has been reported to have efficacy in the treatment of OA pain (Lascelles et al, 2008). Corticosteroid therapy and intraarticular corticosteroids are not recommended for the treatment of canine OA. Intra-articular therapy may provide a temporary remission of clinical signs, however, steroids accelerate the catabolic processes occurring in OA patients, leading to an eventual worsening of the disease process. Other treatments Other documented treatments for use in OA cases include pentosan polysulphate, doxycyline, extracorporeal shockwave therapy, therapeutic ultrasound and acupuncture. For all these treatments there is little, or no, scientific evidence to support their use. In one clinical study hyaluronic acid administered intra-articularly was shown to effect an improvement in dogs with OA, but this has not been reproduced in further studies and the analgesia provided was only temporary (Hellstrom et al, 2003). 4 / 6

5 Conclusion The treatment of OA is complex and requires a multimodal approach (Panel 1). Each dog has very different needs and a good clinician should adapt his or her approach to the individual case. It is vitally important to ensure clients are aware of the necessity to review and alter therapies regularly, and that treatment is in no way a quick fix. Although a number of therapies are available, scientifically proven clinical trials are few and far between and the evidence for a large number of suggested therapies is lacking. Acknowledgements Thank you to Dylan Clements and Marge Chandler for their input and images. All images remain the property of The University of Edinburgh. References and further reading Abercromby R A, Innes J and May C (2006). Arthritis. In BSAVA Manual of Canine and Feline Musculoskeletal Disorders (1st edn), BSAVA, Gloucester. Fox S M and Millis D (2010). Multimodal Management of Canine Osteoarthritis (1st edn), Manson Publishing/The Veterinary Press, London. Hellstrom L E, Carlsson C, Boucher J F and Michanek P (2003). Intra-articular injections with high molecular weight sodium hyaluronate as a therapy for canine arthritis, Veterinary Record 153: Lascelles B D, Gaynor J S, Smith E S et al (2008). Amantadine in a multimodal analgesic regimen for alleviation of refractory osteoarthritis pain in dogs, Journal of Veterinary Internal Medicine 22: Marshall W G, Hazewinkel H A, Mullen D et al (2010). The effect of weight loss on lameness in obese dogs with osteoarthritis, Veterinary Research Communications 34: Millis D L (2006) Nonsteroidal anti-inflammatory drugs, disease-modifying drugs, and osteoarthritis, Veterinary Medicine supplement: Roush J K, Cross A R, Renberg W C et al (2010). Evaluation of the effects of dietary supplementation with fish oil omega 3 fatty acids on weight bearing in dogs with osteoarthritis, Journal of The American Veterinary Medical Association 236: Salter R B, Hamilton H W, Wedge J H et al (1984). Clinical application of basic research on continuous passive motion for disorders and injuries of synovial joints: a preliminary report of a feasibility study, Journal of Orthopaedic Research 1: Sparkes A H, Heiene R and Lascelles B D X (2010). ISFM and AAFP consensus guidelines: long-term use of NSAIDs in cats, Journal of Feline Medicine and Surgery 12: / 6

6 Powered by TCPDF ( Tobias K M and Johnston S A (2012). Veterinary Surgery Small Animal (1st edn), Elsevier Saunders, Missouri. Veterinary Medicines Directorate (www. vmd.defra.gov.uk/). PANEL 1. MULTIMODAL APPROACH OVERVIEW TO MANAGING THE CANINE OSTEOARTHRITIC PATIENT 1. Assess patient, stage the disease and ensure the client is on board. 2. Adopt a weight loss plan for overweight animals. 3. Consider the exercise regime. 4. Provide analgesia (NSAID). 5. Consider nutraceutical supplementation or prescription diet. 6. Monitor clinical response change regime if necessary. 7. Consider further analgesia if breakthrough periods occurring. 8. Consider salvage surgical procedures if conservative therapy fails. 6 / 6