Phenylbutazone

NSAID for musculoskeletal pain, lameness, and inflammation in horses; osteoarthritis, laminitis, and navicular disease; most commonly used equine NSAID. Pyrazolone NSAID (phenylbutazone). Mechanism: non-selective COX-1 and COX-2 inhibitor → reduces prostaglandin and thromboxane synthesis → anti-inflammatory, analgesic, antipyretic. Most common equine NSAID; enolic acid derivative. Highly protein-bound; long tissue half-life in horses. GI ulcerogenicity risk significant with overdose. Key information NSAID (horses, dogs). Do NOT use in horses intended for human consumption. Food and Drug Administration prohibits extra-label use in food horses. Monitor for GI ulceration and right dorsal colitis. Do not exceed recommended dose or duration. Administer with feed to reduce GI effects. Injectable: IV only in horses — IM causes severe tissue necrosis.

Horses — IV: administer slowly into jugular vein (dilute if available; do NOT give IM/SQ — tissue necrosis). Oral granules/paste: Administer orally via dose syringe placed at the back of the tongue, or mix into a small amount of palatable feed. — mix granules into grain or administer paste via dose syringe. Do not allow oral paste to contact oral mucosa directly (ulceration risk). Store at room temperature; protect from light. If a dose is missed Give the missed dose as soon as you remember. If it is almost time for the next dose, skip it. Do not double up. Phenylbutazone should always be given with feed — never on an empty stomach.

GI: gastric and right dorsal colonic ulceration (right dorsal colitis — most significant concern in horses; higher risk than other NSAIDs). Renal: acute tubular necrosis (dehydration). Oral ulceration at paste contact sites (mucous membranes). Hematologic: aplastic anemia, agranulocytosis, thrombocytopenia (rare but serious in dogs — highly toxic species for PBZ). Protein-losing enteropathy. Hepatotoxicity.

For animals Monitor for GI ulceration; use with caution in animals with GI disease. — right dorsal colonic ulceration (horses); gastric ulceration (dogs). Monitor renal function, hydration status, and urine output. Oral ulceration at mucosal contact sites (oral paste). NOT FOR USE IN CATS — severe toxicity. Not approved for use in food-producing animals. Drug interaction: highly protein-bound — displaces other protein-bound drugs. Do not use concurrently with other NSAIDs or corticosteroids. Avoid in geriatric, debilitated, or renally compromised horses. For people handling this medication Wear gloves when handling. Wash hands thoroughly with soap and water after handling. NSAID — potentially serious human health concern: aplastic anemia, agranulocytosis possible with chronic human exposure (especially through paste inhalation or skin contact). Wear gloves when handling. Keep out of reach of children. Pregnant women and women of childbearing age should avoid contact. Do not use in food animals. Keep out of reach of children. Inform your doctor if handling regularly.

Contact your veterinarian or emergency clinic immediately. Overdose causes severe GI ulceration (including right dorsal colitis), kidney damage, and blood cell destruction. IV fluids, GI protectants, and intensive care may be required. Do not give additional doses.