Across the globe cat ownership is on the rise with more than 30% of American households owning at least one feline companion. Over the years improved preventative medicine has extended the lifespan of many companion animal species, including cats, which has led to a large increase in the geriatric population. With age comes many of the same aches and pains we as humans experience such as joint, bone and muscle pain, dental pain, cancer pain, all of which if left untreated can lead to the development of chronic pain states. Enhanced longevity combined with highly perceptive and devoted owners has required veterinarians heighten their awareness to the development of chronic pain associated with certain conditions that can ultimately negatively impact a cat’s quality of life.
Diagnosis of Pain in Cats
Pain in cats can be difficult to diagnose due to the reclusive nature and often sedentary lifestyle many cats have, and is often times misinterpreted as a normal part of aging. Humans with chronic pain states report fear, anxiety, depression, and anger. These emotions are difficult to identify in non-verbal patients, but can be correlated with some of the more common behavioral changes seen in painful cats: aggression, antisocialism, hiding, decreased appetite and weight loss, decreased activity level, and inappropriate urination. In many instances, these common pain-induced behavioral changes develop gradually and can be subtle but are important indicators of pain. Fortunately, the people most familiar with the pet, usually the owner, can detect these subtle changes with ease, making their participation in pain assessment vital.
Feline Pain Assessment Tools
A variety of acute feline pain scales exist today. However, the mechanisms by which acute tissue trauma cause pain differ from those of chronic pain and therefore, limit the utility of these assessment tools. Over the last 20 years, an enormous amount of research has been performed on the subject of pain in feline patients. Much of this research has been directed at how to best treat pain, but focusing on how to accurately assess chronic pain is an essential first step in optimal treatment of pain. The importance of appreciating behavioral indicators of pain coupled with the limitation in chronic pain scales led to the development of owner assessment tool to assess pain in cats.
Currently, the only owner assessment tool developed for use in cats is the Feline Musculoskeletal Pain Index (FMPI). This questionnaire was developed to obtain information from owners regarding their cat’s ability to do various activities compared to what they think a normal adult cat without mobility impairment would be able to do. The score obtained at the end of the survey provides a clinically useful measurement of the patient’s degree of pain. This can then be used to guide appropriate treatment and track pain scores over time.
Feline Pain Management Strategies
Understanding chronic pain conditions have a much different pathophysiology than what occurs in a more acute setting and therefore, require different interventional strategies for optimal pain management in cats is of utmost importance. Additionally, chronic pain requires treatment over an extended period, much of which occurs in the patient’s home, meaning therapeutic approaches will naturally differ from acute pain management.
There are several pharmacologic interventions available for use in cats (Table 1).
Opioids have been used extensively to treat chronic pain conditions in cats. The two and most effective and readily available options are transdermal fentanyl patches and transmucosal buprenorphine. It should be noted that research has shown a high degree of variability in plasma concentrations (analgesic levels of the drug in blood) between cats. This fact requires careful monitoring for signs of inadequate pain control in cats with fentanyl patches in place. Buprenorphine is effective in the treatment of mild to moderate pain in cats and is an excellent option for at home management. Conveniently, its duration of action is long (8-12 hours) allowing for relatively infrequent dosing requirements.
NSAIDs remain the mainstay therapy for patients with various advanced pain states caused by diseases such as osteoarthritis, IVDD, and stomatitis. Long-term use of NSAIDs in cats, particularly those with underlying renal disease, has been a topic of much debate due to the limitations in metabolism of NSAIDs in cats. Cursory investigations into the safety of long-term NSAID use with newer drugs (i.e. Robenacoxib) have shown promising results and has led to licensing approvals in some countries. However, in the United States, Robenacoxib is only labeled for three days or oral dosing. Another commonly prescribed NSAID, meloxicam, has been given a boxed warning by the FDA due to its association with acute renal failure after repeated dosing. Currently this drug is only labeled for one-time intravenous use to treat pain and inflammation associated with orthopedic surgeries, spays, and neuters.
NMDA receptor antagonists have an incredible ability to treat chronic pain through inhibition of excitatory neurotransmitter receptors. Unfortunately, there is limited research into the efficacy of oral formulations (amantadine) in feline chronic pain conditions that has been performed in veterinary medicine. Amantadine has been used anecdotally to improve quality of life for many cats and should be considered as an adjunct to other therapies.
Tricyclic antidepressants (TCAs) have been shown to reduce the severity of neuropathic pain in human patients. The mechanism remains unclear, but is thought to be due in part by its inhibition of noradrenaline reuptake and subsequent activation of alpha-2 adrenergic receptors. No scientific research into the efficacy of this drug class has been performed in veterinary species, however, its limited side-effects make it a relatively safe option as an adjunct therapy in cats with chronic pain due to neuropathy.
Integrative medicine is a well-studied and effective complement to traditional pharmacologic treatment of pain. Modalities such as acupuncture, chiropractic, laser therapy, physical therapy, and massage therapy can all provide immense benefits and drastically improve the quality of life in patients with chronic pain.
Augmenting pharmacology therapies with non-pharmacologic interventions should be considered in every chronic pain patient, particularly when barriers to pharmacologic therapies exist (i.e. renal insufficiency).