Liposomal bupivacaine caudal epidural in horses results in adverse effects without analgesia.

OBJECTIVE

To evaluate the analgesic properties and adverse effects of liposomal bupivacaine administered via caudal epidural in horses.

STUDY

DESIGN

Pharmacodynamic study.

ANIMALS: A total of 10 healthy adult horses.

METHODS

Liposomal bupivacaine (10 mL; 1.3%) was administered into the caudal epidural space via an indwelling epidural catheter inserted to a length of 15 cm. Mechanical nociceptive threshold (MNT) testing with pressure algometry was used to measure analgesia at four anatomic locations for 72 h following injection. Physical examinations (including rectal temperature, heart rate, respiratory rate, and ataxia scores) were performed every 4 h to monitor for adverse effects, and fecal and urine output were recorded.

RESULTS

There were no significant differences detected at any time point in rectal temperature, heart rate, respiratory rate, or MNT at any anatomic site compared to baseline. Ataxia scores were significantly elevated from 24 to 36 h following epidural injection. Adverse events included recumbency in two horses, urinary retention necessitating urinary catheter placement in three horses and decreased fecal output requiring manual manure removal from the rectum in six horses.

CONCLUSION

Liposomal bupivacaine administered as a caudal epidural in horses resulted in ataxia and clinically relevant adverse effects but no detectable analgesia.

CLINICAL SIGNIFICANCE: Based on these findings, caudal epidural administration of liposomal bupivacaine in horses at the dose evaluated in this study is not recommended.