Adding Tapentadol to the Treatment Mix for Osteoarthritis in Horses

Osteoarthritis is a leading cause of chronic pain in horses, responsible for about 60% of all lamenesses. The opioid drug tapentadol was recently examined in horses for treating osteoarthritis-related pain. That report, which was the first study of this medication in horses, showed tapentadol was an effective medication for improving osteoarthritis-related pain.^*

No cure for osteoarthritis currently exists. Instead, treatment options are vast and varied, and include nonsteroidal anti-inflammatory drugs such as phenylbutazone, interleukin-1 receptor agonist protein (IRAP), corticosteroids, regenerative therapies such as stem cells or platelet-rich plasma, tramadol, physical therapies, and oral supplements.

In fact, multiple studies show that oral joint health supplements are among the most popular nutritional supplements used in athletic horses.

“Kentucky Equine Research offers several joint health supplements that offer additional support when combined with a well-balanced diet and management program. When considering a joint supplement, look for products that offer key components such as liquid sodium hyaluronic acid, antioxidants, long-chain omega-3 fatty acids such as EPA and DHA, and the novel omega-6 fatty acid GLA,” shared Catherine Whitehouse, M.S., a nutritionist for Kentucky Equine Research.

In some cases, however, even a multimodal approach cannot sufficiently alleviate the discomfort, making osteoarthritis an important welfare issue. Looking to improve the quality of life of affected horses by finding novel treatment options, Italian veterinary researchers evaluated the efficacy of tapentadol, a synthetic opioid, for osteoarthritis-related pain.

Thirty-six riding horses from one barn were included in the study and divided equally into one of three groups. Group A included horses diagnosed with osteoarthritis and a grade 3 or 4 lameness out of a maximum score of 5 using the American Association of Equine Practitioners lameness scale. Group B included horses diagnosed with osteoarthritis and a grade 5 lameness, and Group C included healthy, sound horses free from osteoarthritis.

Horses in groups A and B were treated with 0.5 mg/kg tapentadol daily for four weeks.

Lameness was evaluated at baseline and then at the end of the week for the four-week study period. Additionally, physiologic variables (heart and respiratory rates), blood biochemistry values, blood cortisol levels, and response to painful stimulation using a modified pain numerical rating scale (NRS) based on the horse’s reaction to flexing the affected joint were evaluated over the course of the study.

“Horses treated with tapentadol had significantly reduced lameness and NRS in all horses with osteoarthritis. Specifically, lameness decreased from baseline values of 3 to 5 in horses with osteoarthritis to 1. Further, NRS decreased from 1 to 3 down to 0 in treated horses,” Whitehouse said.

Circulating cortisol levels, which is a measure of stress, decreased significantly throughout the study period. Cortisol levels were higher in the horses with osteoarthritis at the beginning of the study, but by the end of the four weeks of treatment, cortisol levels were similar between healthy and arthritic horses.

Based on the lower pain scores, cortisol levels, and lameness grade, the researchers concluded, “A tapentadol dose of 0.5 mg/kg is effective for the management of chronic osteoarthritis pain in horses.”

No sedation and ataxia were noted, and no adverse effects of tapentadol were observed based on physiologic and biochemical parameters measured throughout the study.

According to Whitehouse, “Some basic nutrition and management practices that can have a proactive impact on joint health include providing a complete and balanced diet early in life, maintaining an ideal body weight and body condition score to reduce wear and tear on joints, and working closely with your farrier and veterinarian to support conformation and horse comfort.”

Studies also show that offering joint supplements prophylactically prior to any evidence of joint disease may slow the onset of osteoarthritis later in life.

^*Lucrezia Costa, G., M. Tabbì, G. Bruschetta, et al. 2024. Analgesic efficacy of tapentadol in chronic joint disorders in horses: plasma serotonin concentration and adrenocortical response as biomarkers of pain-induced stress. Frontiers in Veterinary Science 11:1505398.