Analgesic efficacy of tapentadol in chronic joint disorders in horses: plasma serotonin concentration and adrenocortical response as biomarkers of pain-induced stress.
Authors: Costa Giovanna Lucrezia, Tabbì Marco, Bruschetta Giuseppe, Spadola Filippo, Leonardi Fabio, Bruno Fabio, Iannelli Nicola Maria, Licata Patrizia, Macrì Francesco, Passino Eraldo Sanna, Macrì Daniele, Interlandi Claudia
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Tapentadol for Equine Osteoarthritis Pain Management Researchers at the University of Messina investigated whether tapentadol—a noradrenaline reuptake inhibitor and μ-opioid receptor agonist—could effectively manage chronic joint pain in horses, using plasma serotonin and cortisol as objective stress biomarkers. Thirty-six horses were stratified by severity: 12 with grade 3–4 osteoarthritis, 12 with grade 5 lameness, and 12 sound controls, receiving either 0.5 mg/kg tapentadol weekly or no treatment for four weeks whilst lameness scoring, pain responses to flexion tests, physiological variables, and blood serotonin and cortisol concentrations were monitored. Both treatment groups showed dramatic improvement, with lameness scores dropping from 3–5 to 1 and pain ratings (modified numeric rating scale) declining from 3–4 to 0 in moderate cases and 4 to 0 in severe cases; notably, circulating cortisol fell significantly post-treatment, whilst serotonin remained stable but remained depressed in arthritic horses compared to controls. For equine practitioners managing chronic lameness, tapentadol appears to offer genuine analgesic benefit beyond placebo, with the added utility of cortisol and serotonin measurements providing objective evidence of pain-induced stress reduction—potentially valuable tools for monitoring treatment efficacy and overall welfare in horses with refractory joint disease.
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Practical Takeaways
- •Tapentadol at 0.5 mg/kg is effective for managing chronic osteoarthritis pain in horses, with lameness improvements evident within the treatment period regardless of initial severity
- •Monitor cortisol levels as an objective marker of pain-related stress reduction during treatment; restoration toward normal cortisol indicates successful pain management
- •Low baseline plasma serotonin may help identify horses with chronic joint pain and poor wellbeing; use this alongside clinical signs to assess pain burden and treatment response
Key Findings
- •Tapentadol 0.5 mg/kg reduced lameness scores from 3-4 to 1 (group A) and 5 to 1 (group B) over 4 weeks of treatment
- •Pain scores on modified NRS decreased from 1-3 to 0 (mild OA) and 4 to 0 (severe OA) with tapentadol treatment
- •Circulating cortisol levels were significantly reduced in tapentadol-treated horses compared to baseline (p<0.001), indicating decreased pain-stress response
- •Plasma serotonin concentrations were significantly lower in OA horses compared to control horses (p<0.001) but did not change during treatment, suggesting potential use as a baseline biomarker for chronic pain state