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

Paracetamol is used in horses alongside non-steroidal anti-inflammatories (NSAIDs) for multi-modal analgesia; however to date there are few studies published which have investigated its analgesic effect in the horse. Horses were recruited to this study from a population of geriatric horses at The Horse Trust. Horses were selected based on the following inclusion criteria; documented naturally occurring chronic lameness and being treated with an NSAID at the licensed dose and dosing interval. This population was assessed with a five-point subjective lameness grading system performed live by two observers and an objective gait assessment tool (EquiGait5). Assessments were performed weekly during the 8-week study period with 2 weeks of baseline assessments. Following this paracetamol was administered for a period of 4 weeks at 20 mg/kg per os twice daily. Paracetamol was then discontinued, and horses monitored for two further weeks. Twenty-five horses were included. Median subjective lameness grade before treatment was 1 (Range: 1-3) and did not change during the treatment period. Interobserver agreement was moderate to very good for forelimb lameness and was moderate to good for hindlimb lameness. There was no statistically significant difference between time points when assessing lameness with the objective gait analysis. In a population of mild chronically lame retired horses receiving NSAIDs, oral paracetamol at 20 mg/kg did not significantly reduce the lameness severity when assessed with both subjective and objective gait analysis.