Chronic Pain in Dogs: The Gift That Keeps on Giving

As the science continues to advance and new treatment choices for OA are developed, there is no doubt our canine patients will reap the benefits

Pain in animals is what we (humans) say it is. There is tremendous variability among both patients and observers. Pet pain is complex and scientifically intriguing, clinically challenging, and easy to overlook.

Studies reveal that approximately 20 percent of dogs across all ages suffer from the chronic maladaptive pain associated with osteoarthritis (OA). The disease causes debilitation and interferes with the activities of daily living. Unfortunately, it is easy for dog owners to overlook OA pain, as they often misinterpret behavior changes as “just getting old,” rather than recognizing a chronic pathological condition that can and should be treated. Managing chronic maladaptive pain in dogs with OA has been a priority in veterinary medicine in recent years, resulting in rapid expansion of the evidence-based components of multimodal pain management strategies.

Slowing the disease progression

Fundamentals of chronic pain management include understanding that treating pain is good medicine, and a multimodal pain management plan is the strategy of choice. Multimodal chronic pain management utilizes multiple actions on the central nervous system (CNS) and other tissue targets to treat and slow OA’s progression. We need to reach for pharmaceuticals, nutrition, physical medicine, and nutraceuticals—all the tools in the pain management toolbox—to manage painful canine patients appropriately. We also need to be sure to start with a comprehensive, hands-on physical examination alongside a metabolic profile to ensure we do not overlook any comorbidities, such as renal disease or hypothyroidism.

For OA patients, inflammation is an important element of their disease. Obesity and being overweight contribute to systemic inflammation, so normalization of body composition is a critical component of reducing inflammation. From a medication perspective, nonsteroidal anti-inflammatory drugs (NSAIDs) remain a cornerstone of multimodal chronic pain management, at least initially. NSAIDs decrease inflammation rapidly, providing immediate relief during the time needed for nutraceuticals to exert their effects. While OA patients derive some benefit from NSAIDs, these drugs alone cannot maximize comfort for patients experiencing chronic maladaptive pain. For that, we need to reach for adjunctive agents.

Gabapentin addresses the maladaptive component of chronic OA pain by targeting the dorsal horn of the spinal cord, where pain signals are modulated on their way to pain perception in the brain. The key to success in using gabapentin for chronic maladaptive OA pain is to use it to effect—that is, escalating the dose to achieve comfort for the dog without inducing sedation. Amantadine is another pharmaceutical affecting the spinal cord that may have a place in a particular patient’s chronic pain plan. Finally, injectable polysulfated glycosaminoglycans (PSGAGs) exert a disease-modifying effect in the body by supporting cartilage structure and joint function. Dosing guidelines for gabapentin, amantadine, and PSGAGs can be found elsewhere. Physical medicine modalities also work adjunctively to help maximize comfort in dogs with OA.

Nutrition and nutraceuticals play a critical role in managing OA pain in dogs. Our canine patients need to eat something each and every day, and that provides a unique way to influence overall health. Good, science-based nutrient profiles allow us to tailor what our patients eat to best meet their individual needs. For painful patients, the most important nutritional step is normalizing body composition. All other pain management strategies work more effectively once body composition is normalized. Likewise, this important step helps to relieve pain and slow OA progression because of a lessened impact on joints. This means using an established nutrient profile in specific portions to achieve the weight target, at which time a proven joint-support formulation may be chosen.

Pain relief through nutraceuticals

Once daily nutrition is in place, canine patients with OA can receive additional pain relief from nutraceuticals, which are nutritional supplements that provide therapeutic benefits yet are not drugs.

There is clear evidence high levels of the omega-3 fatty acid, eicosapentaenoic acid (EPA), in triglyceride form accomplish two major functions in the joint with OA:

1) Decreases inflammation in and around the joint

2) Downregulates the genes responsible for the degradation enzymes that lead to cartilage damage

It is important to understand that flax seed is not an effective source of EPA for dogs. Also, the EPA dose must be high enough to “bottom load” the omega-3/omega-6 ratio and thus reduce inflammatory mediators. While the esterized form of omega-3 fatty acids is less expensive to manufacture, and thus sells for a lower price than the triglyceride form, it is the triglyceride form that is bioavailable.

Microlactin is a milk protein extracted from the milk of hyper-immunized cows. It acts by a very selective mechanism to block cytokines, which contribute to the perpetuation of inflammation. It modifies the biological response to inflammation and changes the signals that “call” neutrophils to sites of inflammation. Thus, neutrophils cannot then release the destructive enzymes that perpetuate the inflammatory process. While it exhibits much the same efficacy as NSAIDs, it employs a different mechanism, so it does not share the same adverse event profile.

Undenatured collagen type II (UC-II) has demonstrated cartilage support effects via immune system modulation. This unique mechanism of action targets Peyer’s patches in the small intestine to stimulate the immune system, generating compounds that block the enzymes responsible for cartilage degradation.

In the U.S., attention is increasingly turning to green-lipped mussel (GLM) extracts, which have demonstrated decreased inflammation and pain associated with OA via multiple tissue targets. While the unique combination of omega-3 fatty acids (EPA, eicosatetraenoic acid [ETA], and docosahexaenoic acid [DHA]) are likely to be a major contributing factor to the anti-inflammatory action, GLM contains a host of furan fatty acids (F-acids), sphingolipids, phytosterols, diacylglycerols, diterpenes, sesquiterpenes, and saponins, alongside antioxidants such as carotenoids, xanthophylls, and anthocyanins. Identifying the overall mechanisms relating to each of these active compounds is the subject of ongoing research. It is certainly possible this combination of ingredients is working synergistically to be chondroprotective, gastroprotective, and anti-inflammatory.

Research suggests GLM may have chondroprotective properties. Studies reveal GLM extracts suppress the same inflammatory pathways affected by NSAIDs, but without their side effect profile. Like many other nutraceuticals providing anti-inflammatory pain relief, GLM is safe to administer long-term, making it well suited for chronic conditions such as OA. There appears to be additional benefit to using GLM, as it has a washout period longer than NSAIDs, still demonstrating effect after four weeks of withdrawal, which is useful in a condition where veterinarians regard owner compliance as the primary barrier in the treatment of chronic pain.

Which is best?

While understanding the individual ingredients in nutraceuticals is important, there are some details we must consider:

  • The most important factor in choosing a nutraceutical is a specific product’s performance in clinical studies in the target species. What matters is how the ingredients work together in a particular formulation in the patients we will treat. This means clinical studies in the target species with the condition we intend to treat (in this case OA in dogs) that demonstrate efficacy and safety in that patient population.
  • Quality assurance is critical. We must understand how nutraceuticals are manufactured, how individual ingredients are sourced or formulated, and what quality control strategies are in place. It is appropriate to seek independent analyses affirming consistency.
  • Ingredient sourcing is also important. For instance, in the case of green-lipped mussels, there is huge variability among populations depending on where and how they are farmed. Understanding that variability, as one example, offers the opportunity to hold manufacturers accountable to provide information about such details.

Managing osteoarthritis in dogs is an evolving discipline. Not many years ago, veterinarians reached for NSAIDs and that was the only thing offered. Within a relatively short time, treatment options for OA expanded dramatically. Nutraceuticals have become an important component of a multimodal pain management strategy for dogs with OA. That said, it is important for veterinarians and their health-care teams to maintain open minds coupled with healthy skepticism, as they evaluate the nutraceuticals they will add to their treatment plans. There is no doubt our canine patients will reap additional benefits as the science continues to advance and new treatment choices are developed.

This bodes well for pets and the people who love them.

Author: Robin Downing, DVM, MS, DAAPM, DACVSMR, CVPP

Link: https://www.veterinarypracticenews.com/supplements-oa-september-2020/

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