Vet Insight: Phenylbutazone and Breakdown Injuries in Racehorses 2025 🏇💊💥

By Dr Duncan Houston, BVSc

The debate over race-day medication continues—and new data adds serious weight to the argument for stricter controls on phenylbutazone use. 🧠💉

A recent study by researcher Teresita Zambruno, covering over 500,000 race starts in South America, has found that horses administered phenylbutazone (bute) prior to racing are significantly more likely to experience breakdown injuries—both fatal and nonfatal. 📉🐎

1. What Are Breakdown Injuries? 💥

Breakdown injuries refer to catastrophic musculoskeletal injuries that occur during racing, often resulting in euthanasia or career-ending damage. Examples include:

• 🦴 Fractures of the cannon bone, sesamoids, or pelvis
• 🧬 Tendon or ligament ruptures
• 🏥 Joint capsule tears with secondary infection

These are among the most tragic and highly scrutinized events in horse racing. ⚠️

2. The Study: What It Found 🧪

The study from the University of Glasgow revealed a 50% increase in injury risk in horses with phenylbutazone in their system on race day. Key points include:

• 📊 Horses with bute were 1.5x more likely to sustain a breakdown injury
• 📈 This is the first large-scale study to show this specific connection
• 📌 Includes both fatal and nonfatal outcomes

This evidence supports growing concerns that pain-masking medications allow injured horses to push beyond their limits, often with devastating consequences. 🧠🐴

3. The Role of Bute: Friend or Foe? 🤔

Phenylbutazone reduces inflammation and pain—but in doing so, it also:

• 🧠 Masks symptoms of musculoskeletal strain
• 🏃 Allows horses to race on sore limbs
• 📉 Delays detection of chronic issues by trainers and vets

This means horses with underlying lameness or fatigue may run full speed despite being on the verge of structural failure. 💥

4. Expert Response from the Jockey Club ⚖️

Dr. Tim Parkin, epidemiologist for the Jockey Club, stated that he now supports zero tolerance for phenylbutazone on race day based on these findings. 🔒

Current U.S. rules:

• ⏳ Bute allowed up to 48 hours before the race
• 🧪 Small amounts permitted in post-race testing

Only California enforces a no-bute-on-race-day rule—and it has seen a reduction in breakdowns since the change. ✅

5. A Word of Caution: Correlation vs. Causation ⚠️

While the study strongly links bute use to higher injury risk, it doesn’t prove bute causes injury directly. Horses receiving bute are:

• 🧓 Often older or in more intense training cycles
• ⚠️ More likely to be managing pre-existing pain

Still, the study raises legitimate concerns about using NSAIDs to prepare horses for high-speed competition. 🧬

6. Ethical Alternatives & Best Practices ✅

To reduce breakdown risk, prioritize:

• 🔬 Full soundness and lameness evaluations before racing
• 📈 Transparent injury reporting and vet checks
• 🧘 Recovery-focused rest, rehab, and training programs
• 🔄 Avoiding “racing through” chronic conditions

Bute should be reserved for post-race recovery or injury management, not as a performance tool. 🧠

7. Summary Table: Bute & Injury Risk 📋⚠️

8. Final Thoughts from Dr Duncan Houston 💬

Racing responsibly means putting horse welfare above race-day wins. As this data makes clear, pre-race bute use could be tipping already vulnerable horses into breakdown territory. Prevention begins with transparency, strict medication policy, and ethical care. 🧠🏇💔

Need help creating a safer race prep plan or reviewing your equine NSAID protocols? Visit AskAVet.com or download the Ask A Vet app 📲 for ethical equine sports medicine guidance and injury prevention strategies.

— Dr Duncan Houston, BVSc