Many Paths to Chronic Equine Pain Management

Growing acceptance of multimodal analgesia for the geriatric horse.

New approaches to pain management in horses may not be new to the world of medicine, but veterinary professionals and horse owners are increasingly embracing the concept of multimodal analgesia, said Alex Bianco, DVM, MS, DACVIM, assistant professor, department of veterinary population medicine at the University of Minnesota College of Veterinary Medicine. “They are recognizing that pain management often requires a creative approach that may include stacking different classes of drugs, bodywork, supplements, and/or podiatry.”

Bianco, who presented sessions on chronic pain management at the VMX 2021 Conference, recently responded to questions about the topic presented by Veterinary Advantage magazine.

Veterinary Advantage: What are the three most common causes/sources of chronic pain in the senior horse?

Dr. Bianco: The most common source of chronic pain in the geriatric horse is likely osteoarthritis (OA). I assume all geriatric horses have osteoarthritis in one or more joints. How much pain the OA causes is highly dependent on the joint(s), severity of disease, and activity/use of the animal. Many geriatric horses also suffer from chronic foot pain, either due to endocrinopathic laminitis or other long-term conditions, such as navicular syndrome (podotrochlosis). A third potential source of chronic pain that is likely more common in the geriatric population is dental disease. These are all a result of degenerative processes that worsen with time (i.e., age).

 

Veterinary Advantage: What has research revealed in recent years concerning the management of chronic pain in the geriatric horse?

Dr. Bianco: Recognition and acknowledgement of pain in veterinary medicine has been an active area of research in the past 10 years. However, the studies in horses have primarily focused on identifying, quantifying and treating acute pain, such as in postoperative or inducible pain models. No studies have specifically focused on evaluating the long-term management of chronic pain in geriatric horses. This is not surprising, given how difficult these studies would be to perform as randomized, controlled, prospective studies.

Research in geriatric medicine has primarily been survey-based, epidemiologic studies or retrospectives of horses presenting to referral hospitals. Still, we have learned that while veterinarians recognize most old horses as lame, owners are not automatically going to recognize lameness. If they do, they may not associate chronic lameness as an indicator of pain. We also know that geriatric horses are less likely to receive regular veterinary care as compared to non-geriatric horses.

 

Veterinary Advantage: Please talk about new approaches to chronic pain management.

Dr. Bianco: Owners have seemingly been quick to accept non-traditional therapies as a beneficial addition to their horse’s care, such as chiropractic adjustment, acupuncture, and other body work, though primarily in their non-geriatric horses. While I am not an expert in these areas and few peer-reviewed studies demonstrate their effectiveness, acupuncture has been shown to be effective in a few studies when used frequently (e.g., multiple times per week). Owners also commonly give their horses nutraceutical supplements despite there being little research or oversight of these products.

 

Veterinary Advantage: What is the current thinking of managing osteoarthritis in horses?

Dr. Bianco: There is no consensus. This is true even in human medicine. What works best for one horse/situation may not work for another. Cost is also a factor. Intra-articular therapy is more expensive than an oral NSAID and may not be a feasible long-term solution for a chronically painful condition. We want geriatric horses to be as comfortable as possible, but we have to consider the budget of the owner as well as the use of the horse.

 

Veterinary Advantage: Any thoughts about the future of equine chronic pain management?

Dr. Bianco: I am excited by the focus on geriatric horses and hope to increase awareness of their needs. I think it is also important to recognize the value of a consistent relationship with a veterinarian, as this is essential in managing chronic pain. Equine practitioners have been open to offering new therapies to their clients and undergoing training in techniques such as chiropractic and acupuncture, which is great. There has been an increase in early recognition and treatment of insulin dysregulation (ID) in horses with PPID and/or EMS. This is important for pain management, as ID often leads to endocrinopathic laminitis, a common cause of chronic pain in older horses that is best managed if prevented altogether.

 

Treatment options

Presenting at the VMX 2021 Conference, Alex Bianco, DVM, MS, DACVIM, assistant professor, department of veterinary population medicine at the University of Minnesota College of Veterinary Medicine, summarized most-often-used and upcoming approaches to chronic pain management in the geriatric horse. Following are some highlights from the conference proceedings.

 

Systemic drugs:

• Non-steroidal anti-inflammatory drugs (NSAIDs): Treatment of pain in horses has traditionally relied on NSAIDs, which inhibit the cyclooxygenase enzymes (COX-1 and COX-2) of the arachidonic acid pathway, decreasing the production of inflammatory mediators and thus reducing pain. These drugs have been approved for use in horses for decades and therefore have the most research supporting their use. One benefit of NSAIDs is that they have no central action, meaning they have little [human] abuse potential. However, this also means that they are ineffective analgesics for conditions without an inflammatory component.
• Opiates: Opioids are effective analgesics that have a central mechanism of action, meaning they have an effect regardless of whether the animal is experiencing pain or inflammation. This is beneficial when the cause of pain is multifactorial or of unknown etiology, but can lead to [human] abuse potential and are impractical for on-farm use.
• Gabapentin: Gabapentin is used to target pain originating from the nervous system. Given its oral formulation and generic option, it has been an important addition to veterinary pain management. Despite few clinical trials in horses, anecdotal reports of its effectiveness are common, usually as part of a multimodal approach. However, a recent study found no effect of gabapentin on reducing chronic forelimb lameness when used alone, and there has been increasing concern for human abuse potential.
• Acetaminophen: While acetaminophen (paracetamol) has been used in human medicine for decades, it has only recently been studied in horses. The literature is limited, but anecdotally, acetaminophen is being used with increasing frequency.

 

Local treatment: Joint injections are common for local treatment of osteoarthritis (OA) in horses, given the ability to safely deliver concentrated doses of medications at the site of the problem. Joint injections in geriatric horses likely depend on their performance level, but no studies were identified that specifically evaluated the use of joint injections in geriatric horses. Given the progressive nature of OA, geriatric horses may be more likely to have end-stage disease, which would make local injection ineffective and/or impossible.

 

Nutraceuticals: Equine nutraceuticals are unregulated by the FDA. Of the countless products marketed towards chronically painful conditions, most have little to no peer-reviewed, published data, and many studies are contradictory.

 

Cannabinoids: Cannabinoid use for chronic pain is promising in humans and is currently being studied in horses and other animals. Recently, an in vitro study identified expression of the target CBD receptor in the dorsal root ganglia of horses, supporting further research into use for chronic pain. However, this is early research and no pharmacokinetic or clinical trials in horses have been reported.

 

Other considerations: Geriatric horses must be treated holistically to manage chronic conditions. Podiatry is considered an essential consideration for horses suffering from chronic pain originating in the foot, namely laminitis and navicular syndrome. An overall assessment of health, including bloodwork and diagnostic testing for pars pituitary intermedia dysfunction (PPID) and insulin dysregulation is recommended. Endocrinopathic testing is essential when managing laminitis, given that risk of PPID increases with age, and the risk of laminitis increases with a diagnosis of PPID.

 

Source: Proceedings, VMX 2021 Conference, Alex Bianco, DVM, MS, DACVIM, assistant professor, department of veterinary population medicine at the University of Minnesota College of Veterinary Medicine

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