Arthritis and Chronic Pain

Recent studies have focused on the chronic pain suffered by arthritic dogs, and have resulted in changes in the way we are treating these pets.
A new tablet medication will make optimal treatment easier.

Osteoarthritis (also called degenerative joint disease) affects one in every five adult dogs, and is the most common cause of chronic pain that veterinarians treat.

Osteoarthritis is a degenerative, progressive and irreversible disease process of the Synovial (fluid) joints. Loss of cartilage from the joint surfaces, and extra bone and fibrosis formed around the joint, result in pain, lameness and loss of joint movement.

Current medications focus on slowing down the loss of joint cartilage and/or stimulating repair. However, recent research has focused on the important role of pain relief in arthritis.

ARTHRITIS AND PAIN

Pain in osteoarthritis is often recognised as an intermittent problem, as owners and vets tend to identify and treat the acute episodes or ‘flare-ups’, often related to over-exercise or similar events. Acute pain plays an important role – it tells the dog ‘slow down’, to prevent further tissue damage and stimulate tissue repair.

In reality, osteoarthritis is a continuous disease process, and as it advances the pain becomes chronic. This chronic pain has an insidious onset that intensifies over time. Initially it may only be present when the joint is moving or weight bearing, and will improve with rest, but as the disease progresses pain is present at rest, and can even affect the pet’s sleep.

The exact mechanism of chronic pain in osteoarthritis is not well understood, but it is recognised that ‘inflammatory mediators’ from the damaged joint are involved in stimulating nerve pathways. When pain receptors are stimulated repeatedly this results in a strong ‘brain memory’, so that the brain will respond more rapidly and strongly to this pain in the future. Once this has happened, larger doses of pain relief medication (analgesics) are required to suppress it.

Chronic pain serves no useful purpose – it does not help tissue repair and only leads to physical and emotional distress. Chronic pain contributes to lameness and muscle wasting, and speeds joint damage. It is now also thought that brain memory of pain can also increase inflammation and further damage in the joint.

The focus of long term management of osteoarthritis should be to prevent ‘brain memory’ of pain through long term continuous pain relief.

NON STEROIDAL ANTI-INFLAMMATORY MEDICATIONS

Non steroidal anti-inflammatory drugs (NSAIDs) have the strongest evidence for efficacy for pain relief (analgesia) in canine osteoarthritis. Commonly used NSAIDs in dogs include Rimadyl®, Bomazeal lnitialize®, Metacam® and Previcox®. NSAIDs act by blocking the activity of inflammatory mediators in the joint.

Recent studies have shown when used long-term to prevent the build up of pain, NSAIDs can also slow the progression of arthritis.

PREVIOUS RESTRICTIONS TO LONG-TERM NSAID USE

Owner questionnaires reveal that only one third of dogs prescribed pain medication by their vets receive the full course. This may simply be because owners forget to give the medication, but there is also evidence that it is difficult for them to assess the level of pain their pet is feeling, resulting in them unintentionally underestimating the pet’s suffering.

Previously, pet owners and vets may have also been wary of the risks associated with long-term NSAID use.

LONG-TERM USE OF NSAIDS

Studies demonstrate that the long-term administration of a NSAID provides a steadily increasing improvement of clinical signs of osteoarthritis in dogs.
In one recent study, the percentage of dogs responding well to treatment increased from 12% on day 5 to 74% on day 120. Similarly, the percentage of dogs not responding to treatment decreased from 86% on day 5 to 22% on day 120.

All NSAIDs can cause undesirable adverse events. The most common are gastrointestinal (inappetance, vomiting and diarrhoea, and rarely gastric perforation), but renal problems are also possible. The low level of adverse effects is reduced further by regular blood monitoring in pets on long-term treatment. Recent studies show that long-term NSAID use does not cause any higher incidence of adverse effects than in dogs on short-term treatment.

Long-term use of NSAIDs bring clinical benefits with a very low risk of serious adverse events.

WHAT IS TROCOXIL ®?

Trocoxil is a new non steroidal anti-inflammatory registered for use in dogs for the treatment of pain and inflammation associated with degenerative joint disease. The drug is uniquely long acting. After an initial loading dose of a tablet given 14 days after the first, it requires only once-monthly tablet administration.

By making it easier to administer longer courses of treatment, Trocoxil addresses the chronic pain challenge and offers dogs the potential of a better outcome.
As a NSAID, the product does carry a small risk of gastrointestinal and renal side-effects. Studies show these are similar to those observed in Rimadyl treated dogs – Trocoxils long half-life is ‘not correlated to the persistence of side-effects.

WHAT ARE THE BENEFITS OF CONTINUOUS NSAID THERAPY?

  • Prevent development of chronic pain
  • Reduced joint inflammation
  • Progressive reduction in pain
  • Reduce number of relapses (flare ups)
  • Slow progression of arthritis
  • No increase in the level of side-effects