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Research Discovery May Enhance Treatment Therapies for Chronic Pain in Pets, People

Clinician scientists in the Comparative Pain Research Laboratory at North Carolina State University’s College of Veterinary Medicine have uncovered a novel method to detect clinically relevant pain relief in cats suffering from Degenerative Joint Disease (DJD). The findings could enhance the ability to test new treatment therapies for pets as well as people who suffer from chronic pain.

The findings are published in the paper, “Detection of Clinically Relevant Pain Relief in Cats with Degenerative Joint Disease Associated Pain,”  in the current issue of the Journal of  Veterinary Internal Medicine.


“We used the commonly observed ‘placebo effect’ phenomenon from clinical practice, and applied it to a clinical trial,” says Duncan Lascelles, the study’s lead investigator and expert on pain and DJD in cats. “We hope to apply the findings from this clinical trial to future study designs”

According to Dr. Lascelles, most clinical drug trials rely on detection of improvement over a placebo, but in trials for pain relief, even in pets, a large placebo effect is often seen.

“This is especially interesting in studies of treatments for pain in veterinary medicine, where subjective outcome measures, like asking caregivers to rate their pet’s level of activity and pain relief, are frequently used,” says Dr. Lascelles.

In the NC State study, people rated their cat’s improvement on measures of activity both on and off of a daily non-steroidal anti-inflammatory medication.

“When we looked at levels of activity and pain relief in active medication versus placebo cats, we did not see a difference in caregiver rating. Both groups were much improved,” says Margaret Gruen, a veterinary behaviorist and lead author on the study. “However, when we looked at the study’s blinded washout phase that followed a treatment period, we found caregivers clearly noticed the return of clinical signs after withdrawal of the active medication, but not after the withdrawal of the placebo.”

“Caregivers of cats that had been on the non-steroidal anti-inflammatory saw their pet’s activity and mobility decline,” says Dr. Lascelles. “In the clinic, we often use a period of drug withdrawal to determine efficacy, but to our knowledge, this has not been applied to a clinical trial design in the past.”

The study involved 66 pet cats that, after physical exams and radiographs conducted by CVM veterinarians, were diagnosed as suffering from DJD, a disease that affects more than 90% of cats the age of nine and older. Critical to the cat’s eligibility was that their caregivers reported that the cat’s mobility was impaired.

Once enrolled, the cats wore a collar-mounted activity monitor and remained in their homes throughout the study. Caregivers were asked at regular intervals about their cat’s ability to perform particular activities, such as jumping up or down, with several questions about activities that were specific to each individual cat.

“Caregivers are often our best measure of improvement in mobility and activities in their cats,” says Dr. Gruen. gruen“Studies have shown that caregivers detect changes in their cat’s ability to perform physical activities and even changes in mood and sociability that may be related to pain. At the same time, the placebo effect is pervasive throughout the literature. This is the first time we have been able to clearly show efficacy, above a placebo, in a trial using caregiver evaluations of their own cats.”

Data later collected from the activity monitors supported the placebo effect.

The Comparative Pain Research Group, founded by Dr. Lascelles in 2007, studies chronic pain and treatment in dogs as well as cats. Studies of novel therapies are ongoing for both species.

“We are excited about the potential breakthrough in the detection of pain relief, and our ability to test new therapies for the many cats and dogs that suffer from chronic pain,” says Dr. Lascalles. “We also believe that this has relevance for development of new treatments for chronic pain in humans, where a large placebo effect also exists.”

“Chronic pain in humans, whether from osteoarthritis or other chronic conditions, is among the leading causes of disability in people,” Dr. Lascelles continues. “Research into treatments for chronic pain in humans has been plagued by the difficulty in showing efficacy over placebo. We believe that this trial design offers a new avenue for demonstrating that efficacy.”