Comparison of analgesic and tissue effects of subcutaneous perineural injection of liposomal bupivacaine and bupivacaine hydrochloride in horses with forelimb lameness induced via circumferential clamp.

The study compares the efficiency and tissue effects of liposomal bupivacaine to bupivacaine hydrochloride when used as an analgesic in horses with artificially induced lameness. The research found that the liposomal bupivacaine was an effective treatment in most cases and held similar duration of analgesic properties as the bupivacaine hydrochloride but further studies are recommended before it can be clinically endorsed for nerve blocks in horses.

Study Design and Methodology

• The experiment involved six mature light-breed horses, all in good health.
• The researchers used a randomized crossover study design. In this method, each horse acted as its own control, with different treatments applied to different limbs in different periods.
• Lameness was artificially induced in the horses using a circumferential hoof clamp, a method known to create reversible lameness.
• The treatment was an abaxial sesamoid nerve block performed by a subcutaneous perineural injection injecting either 10mg of liposomal bupivacaine or bupivacaine hydrochloride.
• The quantitative data on the horse’s gait was measured using a body-mounted inertial sensor system, before treatment and at 30-minute intervals after the treatment.
• The time taken for each horse to recover 85% of its original gait was also recorded.
• After a minimum of four days (the washout period), the procedure was repeated on the alternative limb using the other type of drug than the one used in the first round.
• At the end of the experiment, the palmar digital nerves and perineural tissues were collected for histological examination.

Results of the Study

• The study showed liposomal bupivacaine alleviated induced lameness in five out of six horses.
• The median duration of analgesia was not significantly different between liposomal bupivacaine (4.5 hours) and bupivacaine hydrochloride (3.0 hours).
• However, there was mild inflammation present at three out of 10 injection sites for liposomal bupivacaine, unlike bupivacaine hydrochloride, which didn’t have inflammation at any of the injection sites.

Study Conclusion

• The findings from the study showed that subcutaneous perineural injection of 10 mg of liposomal bupivacaine at the injection site helped in alleviating artificially induced forelimb lameness in most of the horses.
• In terms of dosage, liposomal bupivacaine was found to offer a similar duration of pain relief as bupivacaine hydrochloride.
• Despite the positive findings, further research is required to evaluate the safety and efficacy of liposomal bupivacaine given the mild inflammation observed in the study.