Flunixin meglumine, best known by the brand name Banamine, is one of the most widely used nonsteroidal anti-inflammatory drugs (NSAIDs) in equine veterinary medicine. It is valued for its strong analgesic, anti-inflammatory, antipyretic, and anti-endotoxic properties. Flunixin is especially effective for visceral (abdominal) pain, making it the first-choice drug for equine colic. It is available in injectable, oral paste, and oral granule formulations.
Overview
Flunixin meglumine is a non-selective cyclooxygenase (COX) inhibitor that blocks prostaglandin and thromboxane synthesis. Its anti-thromboxane activity gives it uniquely potent anti-endotoxic effects, which are clinically useful in horses with gram-negative sepsis, severe colic, or post-surgical endotoxemia. The anti-endotoxic effect occurs at a lower dose (0.25 mg/kg) than the full analgesic dose (1.1 mg/kg).
Uses
Veterinarians prescribe flunixin meglumine for the following conditions in horses:
- Colic — first-line analgesic for abdominal pain of various causes
- Endotoxemia — low-dose flunixin mitigates the systemic inflammatory response to bacterial endotoxins
- Ocular inflammation — equine recurrent uveitis (moon blindness) and other inflammatory eye conditions
- Musculoskeletal pain — lameness, soft tissue injuries, post-surgical pain
- Fever — effective antipyretic for infectious or inflammatory causes
- Post-surgical pain management — routine use after colic surgery and orthopedic procedures
Dosage
Always follow your veterinarian’s dosing instructions. General guidelines:
| Indication | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Colic / musculoskeletal pain | 1.1 mg/kg (500 mg for ~450 kg horse) | IV or oral | Every 12-24 hours | Up to 5 days |
| Anti-endotoxic | 0.25 mg/kg | IV | Every 8 hours | As directed |
| Ocular inflammation | 1.1 mg/kg | IV or oral | Every 12-24 hours | As directed |
Available formulations include injectable solution (50 mg/mL) for IV use by a veterinarian, oral paste syringes (1500 mg/syringe), and oral granules for mixing with feed.
Critical administration warning: The injectable form must be given intravenously only. Intramuscular injection causes severe tissue necrosis and creates anaerobic conditions that allow Clostridial bacteria to proliferate, resulting in potentially fatal myonecrosis. Many veterinarians now recommend that horse owners keep only oral paste on hand.
Side Effects
| Common | Serious (Contact Your Vet Immediately) |
|---|---|
| Decreased appetite | Gastric or colonic ulceration |
| Mild GI upset | Right dorsal colitis (potentially fatal) |
| Soft stool | Kidney damage or failure |
| Oral ulceration | |
| Protein-losing enteropathy |
Gastrointestinal ulceration is the most significant risk. Horses are susceptible to NSAID-induced damage in both the stomach and the right dorsal colon. Right dorsal colitis can present as colic, diarrhea, weight loss, ventral edema, and hypoproteinemia. Risk factors include prolonged use, high doses, dehydration, concurrent corticosteroids, and use of multiple NSAIDs.
Flunixin can also mask colic pain so effectively that it obscures progression of a surgical lesion. Always contact your veterinarian during a colic episode, even after administering flunixin.
Drug Interactions
- Other NSAIDs (phenylbutazone, firocoxib, meloxicam): Never combine. Allow a washout period of at least 24 hours when switching.
- Corticosteroids (dexamethasone, prednisolone, triamcinolone): Greatly increases GI ulceration risk.
- Aminoglycoside antibiotics (gentamicin, amikacin): Increased nephrotoxicity.
- Diuretics (furosemide): May worsen renal compromise in dehydrated horses.
Contraindications
Do not use flunixin meglumine in horses with:
- Known GI ulceration or history of right dorsal colitis
- Severe dehydration (correct fluid status first)
- Kidney or liver disease
- Concurrent NSAID therapy
- Known hypersensitivity to flunixin
Storage
- Store at controlled room temperature, 59-86 degrees F (15-30 degrees C).
- Protect injectable solution from light.
- Do not freeze.
- Keep out of reach of children and animals.
Frequently Asked Questions
How fast does flunixin work for colic? IV administration typically provides relief within 15-30 minutes. Oral paste takes 30-60 minutes. Remember that flunixin treats pain but not the underlying cause.
Can I give flunixin and phenylbutazone together? No. Never combine two NSAIDs. This dramatically increases the risk of GI ulceration and kidney damage.
Is flunixin safe for foals? Foals are more susceptible to NSAID side effects. A veterinarian may use flunixin in foals at adjusted doses under close monitoring.
Does flunixin show up on competition drug tests? Yes. Withdrawal times vary by governing body. Consult your veterinarian and competition rules for current guidelines.
This information is for educational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before administering any medication to your horse.