💊 Vet Guide: Side Effects of Bute in Horses | 2025 Safe Use, GI Risks & Right Dorsal Colitis 🐴

By Dr Duncan Houston, BVSc

Phenylbutazone, commonly called **bute**, is one of the most widely used medications in equine medicine. It’s a non-steroidal anti-inflammatory drug (NSAID) used to relieve pain and reduce inflammation from injuries, arthritis, and more. But despite its popularity and availability, **bute is not a harmless “aspirin” for horses**—and misuse can lead to serious, even fatal, complications. 💊🐎

In this 2025 guide, I’ll explain how bute works, its most dangerous side effects, and how to use it safely under veterinary guidance. 🧠🩺

⚖️ What Is Bute & How Does It Work?

Bute belongs to the NSAID class of drugs. It works by **blocking prostaglandins**, chemical messengers that cause pain and inflammation. But prostaglandins also protect the stomach lining and help maintain healthy kidney function—so when we block them, we also risk harming the digestive tract. 🧪

Common Uses of Bute:

• 🦴 Joint pain or osteoarthritis
• 🔗 Tendon or ligament inflammation
• 🐴 Muscle soreness from training or hauling

While effective, it’s not a drug to use “just in case.” Like all NSAIDs, **bute comes with real risks**. ⚠️

🔥 The Most Serious Side Effect: Right Dorsal Colitis

One of the most dangerous complications of bute is **Right Dorsal Colitis (RDC)**—a severe inflammation of the upper right portion of the horse’s colon. This occurs when bute disrupts the protective lining of the gastrointestinal (GI) tract, allowing acid and toxins to damage the tissue. 🧠

Key Facts About RDC:

• 📉 Causes **protein loss** into the gut (protein-losing enteropathy)
• 🩸 Can lead to **severe colic, diarrhea, and laminitis**
• ☠️ May be **fatal** in extreme cases

Unfortunately, RDC can occur even at **recommended dosages**, particularly in horses with other risk factors. ❗

💧 Risk Factors for NSAID Complications

Never Give Bute If Your Horse Is:

• 💧 **Dehydrated** – increases the risk of kidney and gut damage
• 🥱 Off feed or experiencing colic
• 🧪 Already on another NSAID like Banamine (flunixin)
• 🧬 Diagnosed with kidney or liver disease

Even healthy horses can develop problems if dosed too high or too long. **Always use the lowest effective dose** for the shortest duration. 🧠

📉 More Side Effects to Know

Other potential side effects of bute include:

• 🔥 Gastric ulcers or stomach irritation
• 🧬 Kidney damage in dehydrated horses
• 💩 Diarrhea or colitis (beyond RDC)
• ⚠️ In rare cases, **blood disorders** or anemia

Never assume a horse is “fine on bute” just because they’ve taken it before. **Monitor carefully** for any signs of discomfort, colic, inappetence, or swelling. 🧪

🔬 How to Use Bute Safely

Because of its risks, bute should only be used under **veterinary direction**. It’s a **prescription medication**, and for good reason. 📜

Safe Use Checklist:

• 📋 **Always confirm the diagnosis** before administering
• 🧪 Use **bloodwork** in older horses or those with known health issues
• 📆 Don’t exceed **5–7 days** without veterinary oversight
• 🩺 Avoid combining with other NSAIDs or corticosteroids
• 💧 Ensure **hydration is adequate** before use

If your horse needs long-term pain relief, your vet may recommend alternatives like **Equioxx (firocoxib)**, which has fewer GI side effects. 💊

📲 Use Ask A Vet for Medication Guidance

The Ask A Vet app helps you navigate equine medication use with confidence:

• 📋 Ask about safe dosing protocols or alternatives
• 📱 Report side effects like diarrhea or behavior change
• 🧠 Track NSAID usage and vet instructions in one place
• 🔄 Discuss long-term pain plans for chronic arthritis or laminitis

Peace of mind—delivered. 🐴📲

✅ Bute Safety Takeaways for 2025

• 💊 Bute is effective—but **not harmless**
• 🔥 **Right Dorsal Colitis** is a life-threatening side effect, even at normal doses
• 💧 Avoid use in **dehydrated or sick horses**
• 📉 Use **only under veterinary guidance**, at the lowest effective dose
• 📱 Use Ask A Vet to evaluate pain relief options and monitor safety

📲 Final Thoughts from Dr Duncan Houston

Bute can be a powerful ally in equine medicine—but only when used wisely. Treat it like the prescription drug it is, and never assume it’s as simple as “a couple of grams to take the edge off.” Your horse’s gut, kidneys, and life may depend on it. 🧠💙

Download the Ask A Vet app for safe dosing, medication planning, and trusted support for managing pain in your horse. 🐎📱