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Equine veterinary journal2026; doi: 10.1002/evj.70298

Epidural 0.125% ropivacaine is safe but insufficient for induced tibiotarsal joint pain.

Abstract: Epidural injection of a low concentration of the local anaesthetic ropivacaine produces analgesia without neurological deficits or ileus in people. Objective: To determine if epidural 0.125% ropivacaine mitigates induced hindlimb lameness in horses while preserving neurological function and gastrointestinal (GI) motility. Methods: Randomised, blinded, controlled, crossover study. Methods: Eight healthy, sound horses underwent two treatments in random order, separated by at least 3 weeks: epidural saline or epidural ropivacaine. For each treatment, an epidural catheter was inserted at the first intercoccygeal space and advanced 5 cm cranially. Correct catheter placement was confirmed radiographically after injecting contrast through it. The tibiotarsal joint was injected with 75 ng of recombinant equine interleukin-1β to induce synovitis. Twelve hours later, baseline variables were recorded, including heart rate, respiratory rate, borborygmi, lameness score and neurological examination score. Thirty minutes thereafter [time = 0 h (t0)], 0.045 mL/kg of preservative-free 0.9% saline or 0.125% ropivacaine was administered through the catheter over 10 min. Data were collected at t0.5, 1, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5. Faecal piles passed the 24 h before and after t0 were counted. Continuous and categorical data were analysed using a linear mixed effects model and Fisher's exact test, respectively, with significance set at p < 0.05. Results: All horses developed moderate-to-severe lameness that did not improve after ropivacaine injection. No horses developed hindlimb neurological deficits. However, from t0.5-2.5, more horses in the ropivacaine (7/8) than saline (0/7) treatment had decreased to absent anus and tail tone (p = 0.014). There were no other significant differences between treatments. Conclusions: A single volume, concentration, and injection rate were tested. Conclusions: A single dose of 0.125% ropivacaine did not mitigate hindlimb lameness. Anus and tail tone decreased, but hindlimb neurological function and GI motility were preserved.
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Publication Date: 2026-08-17 PubMed ID: 42608338DOI: 10.1002/evj.70298Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study tested whether a low concentration (0.125%) of epidural ropivacaine could reduce induced hindlimb pain in horses without causing neurological problems or affecting gastrointestinal function.
  • The researchers found that while ropivacaine was safe and did not impair neurological or GI functions, it did not relieve the induced joint pain and lameness in the horses.

Background and Purpose

  • Ropivacaine is a local anesthetic used epidurally to provide pain relief; lower concentrations are thought to reduce side effects while providing analgesia.
  • In humans, low-concentration epidural ropivacaine can produce pain relief without neurological deficits or gastrointestinal complications like ileus (loss of bowel motility).
  • The study aimed to determine if this concentration (0.125%) of epidural ropivacaine would effectively reduce pain caused by induced tibiotarsal joint inflammation in horses, without causing neurological or gastrointestinal side effects.

Study Design and Methods

  • The study was a randomized, blinded, controlled, crossover trial involving 8 healthy horses.
  • Each horse received two treatments in random order with a washout period of at least 3 weeks between treatments:
    • Epidural saline (control)
    • Epidural 0.125% ropivacaine
  • An epidural catheter was placed at the first intercoccygeal space and advanced 5 cm cranially; placement was confirmed by radiography with contrast injection.
  • Pain was induced by injecting recombinant equine interleukin-1β into the tibiotarsal joint to cause synovitis, simulating joint pain and lameness.
  • Twelve hours after induction, baseline physiological and clinical data were recorded, including:
    • Heart rate and respiratory rate
    • Borborygmi (intestinal sounds) indicating GI motility
    • Lameness score and neurological examination score
  • Thirty minutes later (designated time 0 or t0), either ropivacaine or saline was administered epidurally over 10 minutes at a dose of 0.045 mL/kg.
  • Data were collected at several time points after injection (0.5, 1, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5 hours), and fecal output was measured over 24 hours before and after treatment to assess GI motility.
  • Data analysis involved linear mixed effects models for continuous data and Fisher’s exact test for categorical data, with significance defined as p < 0.05.

Results

  • All horses developed moderate-to-severe lameness after joint inflammation induction, confirming successful pain model creation.
  • Ropivacaine treatment did not improve lameness compared to saline, indicating that 0.125% ropivacaine epidural did not mitigate the induced joint pain.
  • No horses showed hindlimb neurological deficits with either treatment, indicating neurological safety at this dose/concentration.
  • However, from 0.5 to 2.5 hours after injection:
    • 7 out of 8 horses given ropivacaine developed decreased to absent anus and tail tone (a sign of some local neurological effect), while none of the saline-treated horses did (p = 0.014).
  • Other physiological parameters such as heart rate, respiratory rate, borborygmi, and fecal output showed no significant differences between treatments, indicating preserved gastrointestinal motility.

Conclusions and Implications

  • The tested single dose, volume, and injection rate of epidural 0.125% ropivacaine was safe in horses, not causing hindlimb neurological deficits or affecting GI motility.
  • Despite safety, this concentration was ineffective at reducing joint pain and lameness induced by intra-articular interleukin-1β injection.
  • The decrease in anus and tail tone suggests some local effect on nearby nerves without broader neurological impairment.
  • These findings suggest that while low-dose epidural ropivacaine is safe, it may be insufficient alone for pain relief in equine joint conditions; higher concentrations, different dosing, or adjunct analgesics might be needed.
  • Further research may explore dosing regimens or combinations that balance efficacy and safety for epidural analgesia in horses.

Cite This Article

APA
Boesch JM, Perkins GA, Todd-Donato AB, Colbath AC. (2026). Epidural 0.125% ropivacaine is safe but insufficient for induced tibiotarsal joint pain. Equine Vet J. https://doi.org/10.1002/evj.70298

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Boesch, Jordyn M
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Perkins, Gillian A
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Todd-Donato, Amy B
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Colbath, Aimee C
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.

Grant Funding

  • Harry M. Zweig Memorial Fund for Equine Research

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