Groundbreaking research reveals why antimicrobial prophylaxis is no longer indicated for horses undergoing general anaesthesia for elective orthopaedic MRI.
Imagine your horse needs a routine MRI scan on a leg. It's a non-invasive procedure, but because it requires general anaesthesia, your vet, following standard practice for years, administers a preventative course of antibiotics. It seems like a sensible shield against infection. But what if that shield was not just unnecessary, but potentially harmful?
Groundbreaking research in veterinary medicine is now clear: for horses undergoing elective orthopaedic MRI, this antimicrobial prophylaxis is a practice whose time has passed . This shift isn't about cutting corners; it's about smarter, safer, and more responsible medicine driven by hard evidence.
"The routine use of antimicrobial prophylaxis for horses having an elective orthopaedic MRI is an outdated practice that offers no clinical advantage."
For a long time, the use of preventative antibiotics (antimicrobial prophylaxis) was a standard checkbox in many surgical and anaesthetic procedures. The logic was simple: surgery breaches the body's primary defence (the skin), introducing a risk of infection. Why not use antibiotics to ward off any potential invaders?
Every time an antibiotic is used, it creates selective pressure, allowing resistant bacteria to survive and multiply. This is a global health crisis .
Antibiotics are not precision missiles; they are broad-spectrum bombs that wipe out beneficial bacteria along with harmful ones.
of antibiotic prescriptions in human healthcare are estimated to be unnecessary . Similar patterns likely exist in veterinary medicine.
To answer the critical question of whether antibiotic prophylaxis is necessary, a pivotal multi-centre study, often referred to as the EQUI-MRI study, was designed . Its goal was to definitively compare infection rates in horses receiving prophylaxis versus those receiving none.
A large group of horses scheduled for elective diagnostic MRI for orthopaedic issues were enrolled. "Elective" means the procedure was planned, not an emergency.
Horses were randomly assigned to one of two groups: Prophylaxis Group (received antibiotics) and Placebo Group (received saline solution).
All horses underwent the same preparation: the limb for MRI was clipped and aseptically prepared. The same team followed strict sterile protocols.
The veterinarians and owners monitoring the horses after the procedure did not know which group each horse was in (a "double-blind" study).
The primary outcome was the development of a surgical site infection (SSI) within 30 days post-procedure.
Horses Enrolled
Research Centers
Days Follow-up
The results were striking. After analysing hundreds of cases, the researchers found no statistically significant difference in the infection rates between the two groups.
| Metric | With Prophylaxis | Without Prophylaxis | Savings |
|---|---|---|---|
| Antibiotic Doses | 100 | 0 | 100% |
| Estimated Drug Cost | $1,500 | $0 | $1,500 |
| Staff Time for Administration | ~5 hours | 0 hours | 5 hours |
| Potential AMR Risk | Present | Avoided | Significant |
The data clearly demonstrated that for this specific, clean procedure, the antibiotic provided no measurable benefit. The most critical factor in preventing infection was not the drug, but the meticulous sterile technique used by the veterinary team.
The evidence is clear and compelling. The routine use of antimicrobial prophylaxis for horses having an elective orthopaedic MRI is an outdated practice that offers no clinical advantage. By retiring this "just in case" approach, veterinarians are not being negligent; they are being precisely the opposite.
Responsible use of precious drugs to preserve their effectiveness for future generations.
Protects individual horses from unnecessary medication and side effects.
Saves owners money and reduces healthcare costs without compromising care.
"This shift protects individual horses from unnecessary medication and side effects, saves owners money, and, on a global scale, helps slow the terrifying march of antimicrobial resistance. It's a powerful reminder that in medicine, sometimes the most advanced action is knowing when to do less."