Prevail is a brand-name injectable pain and anti-inflammatory medication for horses. Distributed by MWI Veterinary Supply under the VETone label and manufactured by Norbrook Laboratories, it contains flunixin meglumine as its active ingredient, the same compound found in the well-known brand Banamine. Each milliliter of Prevail delivers 50 mg of flunixin. It is labeled for two primary uses: relieving inflammation and pain from musculoskeletal problems, and easing the deep abdominal pain associated with colic.
How Prevail Works
Flunixin meglumine belongs to the class of nonsteroidal anti-inflammatory drugs, commonly called NSAIDs. It works by blocking an enzyme system called cyclooxygenase, which is a key driver of the body’s inflammatory response. When that enzyme is suppressed, the horse produces fewer of the chemical signals that trigger swelling, pain, and fever. This gives Prevail three overlapping effects: it reduces inflammation in joints, muscles, and soft tissues; it lowers fever; and it provides significant pain relief.
Among equine NSAIDs, flunixin meglumine is considered one of the most effective options for visceral pain, which is the type of pain that originates from internal organs rather than from bones or muscles. That’s why it has become a go-to choice during colic episodes, where a horse’s gut is in distress.
Common Uses
Prevail’s label covers two broad categories, but in practice those categories encompass a wide range of situations horse owners encounter.
For musculoskeletal issues, veterinarians may reach for Prevail when a horse is dealing with lameness from a soft-tissue injury, joint inflammation, or post-surgical swelling. It helps the horse move more comfortably during the acute phase of an injury while other treatments or rest take effect.
For colic, Prevail can quickly take the edge off abdominal pain, which makes the horse easier to examine and less likely to injure itself by rolling or thrashing. However, this pain relief comes with an important caveat: by masking how much pain the horse is actually in, flunixin can make it harder to judge whether the colic is worsening and whether surgery might be needed. If your horse colics and you give Prevail (or any flunixin product), keeping close watch for returning or escalating signs of pain is critical.
Dosage and Administration
Prevail is an injectable solution given intravenously. The standard dose is calculated by the horse’s actual body weight, and accuracy matters. USEF guidelines specify a maximum of 0.5 milligrams per pound of body weight in any 24-hour period. For a typical 1,000-pound horse, that works out to a maximum of 500 mg per day. Treatments are generally given once daily, and most courses last no more than five consecutive days.
Estimating weight by eye is one of the most common ways horse owners accidentally overdose NSAIDs. A weight tape or, ideally, a livestock scale gives a much safer starting point for calculating how much to draw into the syringe.
Side Effects and Risks
The biggest concern with Prevail, as with all flunixin-based products, is damage to the gastrointestinal tract. NSAIDs reduce the production of the protective mucus lining inside the stomach. With repeated or prolonged use, this leaves the stomach wall exposed to its own acid, making ulcers significantly more likely. Research from UC Davis identifies flunixin meglumine (along with phenylbutazone and ketoprofen) as one of the NSAIDs most associated with equine gastric ulcer syndrome.
Horses that are already prone to ulcers, those under heavy training stress, or those on restricted turnout face higher risk. If anti-inflammatory treatment needs to continue beyond the short term, some veterinarians switch to a newer, more stomach-friendly NSAID such as firocoxib. Kidney stress is another potential issue, particularly in horses that are dehydrated or receiving other medications that affect kidney function. Keeping a horse well-hydrated during any NSAID course helps protect the kidneys.
Competition and Withdrawal Times
Flunixin meglumine is a controlled substance under most equestrian governing bodies, meaning it is permitted at certain levels but regulated. Under 2026 USEF rules, no part of a dose should be given during the 12 hours before competition. USEF also notes that flunixin is generally detectable in testing for about three days after administration, so competitors often plan a wider buffer to avoid a positive test.
FEI and other international federations have their own detection times and thresholds, which can differ from USEF. If you compete under multiple organizations, check each one’s current drug rules separately. Detection times can vary depending on the individual horse’s metabolism, the dose given, and the sensitivity of the testing laboratory, so the published guidelines represent minimums rather than guarantees.
Prevail vs. Banamine
Prevail and Banamine are therapeutically equivalent. Both contain flunixin meglumine at the same concentration (50 mg/mL), and both are FDA-approved for the same indications in horses. The difference is branding and distribution: Banamine is made by Merck Animal Health, while Prevail is made by Norbrook and distributed through MWI/VETone. Prevail is often priced lower, which is why many veterinarians and barn managers stock it as a cost-effective alternative. There is no clinical reason to prefer one over the other.