Phenylbutazone (Bute) Vet Guide 2025 – Dr Duncan Houston 🐴💊

By Dr Duncan Houston, BVSc – professional insight into safe, effective use of phenylbutazone in equine care.

Introduction

Phenylbutazone—commonly known as “Bute”—is one of the most widely used NSAIDs in equine veterinary medicine. 💊 It provides effective relief for musculoskeletal pain, fever, and inflammation. This 2025 guide covers its forms, administration, dosing, side effects, contraindications, and best practices. Whether you’re managing an active athlete or caring for a senior horse, this comprehensive resource will ensure safe and informed use of Bute. 🐎

✅ What Is Bute & How It Works

Bute is a non-selective NSAID that inhibits both COX‑1 and COX‑2 enzymes, thereby reducing prostaglandin-mediated inflammation, pain, and fever—though also increasing the risk of gastrointestinal and renal side effects :contentReference[oaicite:3]{index=3}. It’s available in multiple formulations: oral paste, powders, tablets, injectable solution, and bolus :contentReference[oaicite:4]{index=4}.

🛠️ Common Uses

• Lameness, tendon/ligament injury, soft-tissue soreness :contentReference[oaicite:5]{index=5}
• Osteoarthritis and joint inflammation :contentReference[oaicite:6]{index=6}
• Laminitis and hoof-related pain :contentReference[oaicite:7]{index=7}
• Antipyretic use to reduce fever (must be monitored) :contentReference[oaicite:8]{index=8}

🧴 Formulations & Administration

• Paste: Dosed by weight, placed on the tongue—works within 30–60 minutes; peaks in 6 hours :contentReference[oaicite:9]{index=9}.
• Powder/tablet/bolus: Mixed with feed; often preferred for long-term conditions :contentReference[oaicite:10]{index=10}.
• Injectable (IV only): Used for rapid effect; never IM due to tissue necrosis risk :contentReference[oaicite:11]{index=11}.

📏 Dosage Guidelines

Standard dosing:

• Oral dosing at 2.2–4.4 mg/kg/day (typically split into 2 equal doses) :contentReference[oaicite:12]{index=12}.
• IV dosing: 0.5–1 g per 250 kg (2.5–5 mL of 200 mg/mL) daily, max 20 mL/day and no more than 5 days IV :contentReference[oaicite:13]{index=13}.
• High doses (up to 8.8 mg/kg) for laminitis—only under strict vet supervision :contentReference[oaicite:14]{index=14}.

Single daily dosing may be effective due to prolonged anti-inflammatory action :contentReference[oaicite:15]{index=15}.

⚠️ Side Effects & Risks

• GI issues: ulcers, right dorsal colitis causing diarrhea, weight loss, lethargy :contentReference[oaicite:16]{index=16}.
• Renal papillary necrosis and kidney impairment :contentReference[oaicite:17]{index=17}.
• Bone marrow suppression: anemia, leucopenia :contentReference[oaicite:18]{index=18}.
• Oral ulcers and stomatitis (especially with paste or bolus) :contentReference[oaicite:19]{index=19}.
• Potential liver toxicity or jaundice :contentReference[oaicite:20]{index=20}.
• Edema from protein loss due to GI damage :contentReference[oaicite:21]{index=21}.
• IM injection risk: severe inflammation and clostridial myositis :contentReference[oaicite:22]{index=22}.

🔄 Drug Interactions & Contraindications

• Avoid concurrent NSAIDs (e.g., flunixin, firocoxib) or corticosteroids—risk of additive toxicity :contentReference[oaicite:23]{index=23}.
• Caution with anticoagulants due to bleeding risk :contentReference[oaicite:24]{index=24}.
• Contraindicated in horses with kidney, liver, or GI disease :contentReference[oaicite:25]{index=25}.
• Use carefully in pregnant, very young, or elderly horses :contentReference[oaicite:26]{index=26}.
• Not for food animals—illegal in lactating or slaughter-bound horses :contentReference[oaicite:27]{index=27}.

🩺 Monitoring & Safe Use

• Use lowest effective dose for shortest time
• Administer with food to minimize GI upset :contentReference[oaicite:28]{index=28}.
• Regular blood tests: CBC, kidney & liver values
• Monitor for appetite, diarrhea, weight, coat changes, oral ulcers
• Ensure hydration—provide constant access to clean water

♻️ Special Considerations for Paste Form

Oral paste is rapidly absorbed but may irritate oral tissues. Ensure dry mouth before dosing. Maintain oral hygiene. :contentReference[oaicite:29]{index=29}

🚫 Injectable Risks

Only administer IV, never IM. IM administration may cause necrosis, abscess, and clostridial myositis—dangerous and potentially fatal. :contentReference[oaicite:30]{index=30}

📈 Duration & Withdrawal Times

Bute has a plasma half-life of 4–8 hours but inflammatory action lasts 24 hours. Residues can persist—track doses carefully in competing horses. :contentReference[oaicite:31]{index=31}

🧭 Quick Guide Table

🏥 Practical Tips for Owners

• Keep a small emergency supply of paste/powder—but only use under vet guidance
• Prefer oral forms for long-term management
• Never self-dose—always weigh your horse and double-check calculations
• Monitor response—if no improvement in 48 hrs, contact the vet
• Document start/stop dates and any co-medications

🌟 Alternatives & Complementary Options

For chronic pain management, consider COX‑2 selective NSAIDs (e.g. firocoxib/Equioxx), joint supplements (e.g. glucosamine), physical rehab, acupuncture, and weight management :contentReference[oaicite:32]{index=32}.

📲 Ask A Vet Support & Conclusion

Phenylbutazone remains a powerful and widely used tool in equine medicine—but it demands respect. With careful dosing, monitoring, and vet oversight, Bute can significantly improve comfort and mobility. Using the right form, timing, and duration ensures safety. If you’re unsure about dosing protocols, side effects, or combining with other medications, Ask A Vet is ready to help 24/7.

📲 Download the Ask A Vet App today for tailored dosage calculators, reminders, and expert consultations—ensuring every dose of Bute is administered with confidence and care. 🐎