Quantifying the Equine Pain Response to Paracetamol Administration in Horses With Chronic Lameness Already Receiving Non-Steroidal Anti-Inflammatories.

Overview

• The study investigated whether adding paracetamol to non-steroidal anti-inflammatory drugs (NSAIDs) improves pain relief in horses with chronic lameness.
• Results showed that paracetamol did not significantly reduce lameness severity in horses already receiving NSAID treatment.

Study Background and Purpose

• Horses with chronic lameness often experience ongoing pain that limits their movement and quality of life.
• NSAIDs are commonly used to manage equine pain, but there is interest in multi-modal analgesia, which combines drugs for improved effect.
• Paracetamol (acetaminophen) is sometimes added alongside NSAIDs in horses, but evidence of its effectiveness in this context is limited.
• The study aimed to quantify the pain response to paracetamol when given to horses already receiving NSAIDs for chronic lameness.

Study Design and Methods

• Participants: 25 geriatric horses with natural chronic lameness from The Horse Trust refuge.
• Inclusion criteria: documented chronic lameness and ongoing treatment with licensed NSAID doses.
• Assessment tools:
  • Subjective lameness grading on a 5-point scale performed live by two observers.
  • Objective gait analysis using the EquiGait5 system to quantify lameness parameters.
• Study timeline:
  • 2-week baseline period with no paracetamol, assessing existing lameness status.
  • 4 weeks of oral paracetamol administration at 20 mg/kg twice daily, in addition to ongoing NSAIDs.
  • 2 weeks post-treatment monitoring period with paracetamol discontinued.

Key Findings

• Median initial subjective lameness grade was low (1 out of 5), ranging from mild to moderate lameness (1-3).
• Subjective assessments showed moderate to very good agreement between observers for front limb lameness, and moderate to good agreement for hind limb lameness, supporting reliability of observations.
• Throughout the treatment period, no significant improvement in lameness scores was detected either by subjective grading or objective gait metrics.
• This suggests that adding paracetamol at the tested dose and schedule did not provide additional measurable analgesic benefit over NSAIDs alone in this population.

Interpretation and Implications

• The findings indicate that in mildly to moderately lame horses already receiving NSAIDs, paracetamol may not further reduce pain or improve limb function.
• The study advances understanding of analgesic strategies by providing controlled clinical data on paracetamol’s limited effect in this setting.
• Limitations include the mild severity of lameness in the sample, which may have limited the ability to detect subtle improvements.
• Future research might explore other doses, longer treatment durations, or populations with more severe lameness to fully assess potential benefits.
• Clinicians should consider these findings when designing pain management plans and be cautious about expecting additional analgesia from paracetamol in horses stabilized on NSAIDs.