Veterinarians often give penicillin to horses during surgery to prevent infection, but the speed of injection may influence how the horse’scardiovascular system reacts. In a study of 29 horses under general anesthesia, researchers compared two methods of giving penicillin: a fast injection over one minute and a slower one over ten minutes.
Syringes used for giving horses injections.
In equine anesthesia, every decision—from drug choice to administration technique—should prioritize minimizing patient risk.
© 2018 by Fabio Berti New window.
Both methods caused a drop in blood pressure, but the fast injection led to a more dramatic decrease. The slower, more diluted injection resulted in a gentler decline, suggesting it may be safer during surgery. Sudden drops in blood pressure during surgery can be risky. This study suggests that slowing down the penicillin injection and diluting it more could help keep horses safer under anesthesia. These findings highlight the importance of not just what medication is given, but how it’s administered.
Another Ontario Veterinary College (OVC) study comparing two lidocaine infusion protocols to further explore how intraoperative management affects cardiovascular stability and recovery quality is also soon to be published.
“In equine anesthesia, every decision—from drug choice to administration technique—should prioritize minimizing patient risk. Our goal is always to support the horse in all phases of anesthesia (from induction to full recovery) to achieve optimal outcomes,” said Dr. Alexander Valverde, Professor, DVM, DVSc., Diplomate ACVAA at OVC.
Research Paper:
Henderson ARP, Valverde A, Marchiori J, Tisotti T, Torrent A, Côté N, Gomez DE. Effect of rapid and slow intravenous injection of sodium penicillin on arterial blood pressure in isoflurane-anesthetized horses during surgery. Vet Anaesth Analg. 2025 Mar-Apr;52(2):200-207. doi: 10.1016/j.vaa.2025.01.001. Epub 2025 Jan 6. PMID: 39863515.
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Story by: Jackie Bellamy-Zions, Equine Guelph - Press release by Amy Sales