Flunixin meglumine is a nonsteroidal anti-inflammatory drug not related to the corticosteroids, but pharmacologically related to phenylbutazone, aspirin, indomethacin or dipyrone, and the other NSAID (nonsteroidal anti-inflammatory) agents. It also has analgesic (pain-relieving) and antipyretic (fever-reducing) activity, which is secondary to its anti-inflammatory effect. The drug acts directly at the level of the tissues, not via a nervous system action. It acts primarily on inflamed tissues and is used for muscle or bone/joint diseases and in the treatment of colic pain.

Colic. Flunixin meglumine is reported to be quite effective in some cases of colic, although certainly not in all. The cause of the colic must be determined and treated to effect good response.

NOTE. In this author’s experience, flunixin meglumine is most effective in treating cases of chronic, recurrent colic probably related to previous intestinal damage from parasites. The reason for this is not clear and other veterinarians may have other experiences.

Musculoskeletal” Flunixin meglumine is recommended for the treatment of a wide variety of muscular and skeletal disorders. It is recommended that initial treatment be intravenous or intramuscular, followed by oral preparations. The response to treatment may vary with individual horses or with specific conditions; as with any anti-inflammatory preparation, this is to be expected and reflects individual variations in drug response. It is not a reflection on the efficacy of the product per se.

Anti-inflammatory drugs do not “cure” musculoskeletal problems. They do control the inflammation, thereby helping to decrease the ultimate damage and scarring, and making the horse more comfortable during the painful periods.

Pain and inflammation control also serves to make movement more comfortable, thus helping to prevent any permanent decrease in the range of motion of affected areas by preventing them from becoming too “scarred down.” However, pain control/exercise must be carefully counterbalanced with the veterinarian’s instructions regarding limitation of stress to avoid reinjury or worsening injury to damaged areas.

Flunixin meglumine is absorbed well from the gastrointestinal tract and is available as either a granule or paste. The recommended oral dosage is 0.5 mg/lb of body weight or 500 mg/1000 Ib of body weight. Onset of activity is within 2 hours of administration.

Flunixin meglumine is also available as an intravenous injection. Dosage is the same \0.5 mg/lb of body weight), and may also be given intramuscularly. Onset of activity is within 2 hours of administration, with peak response between 12 and 16 hours after administration.

DO NOT USE FOR MORE THAN FIVE CONSECUTIVE DAYS. This product is not intended for long-term use. If significant problems continue after the acute treatment period, consult your veterinarian for advice on further treatment or management techniques. Inadvertent intra-arterial (into an artery) injection can cause ataxia, incoordination, hyperventilation, agitation, and weakness.

To be effective, the full dose must be consumed. Most horses will readily accept the drug when mixed in with their regular feed. Feed must be “moist” (e.g., sweet feed or mash) to avoid the drug settling out to the bottom of the feed bin. For horses that will not take the medicated grain, try mixing the medication in a small amount of molasses and adding this mixture to the grain.

Prolonged oral dosing at high dosages can produce gastrointestinal ulcers in other species and may be expected to do so in the horse, especially foals. No toxicity was observed even at three times the recommended dose for twice the recommended treatment period, using the intravenous route. NO side effects are reported except for local irritation when injecting three times the recommended dose intramuscularly. There have also been isolated reports of marked local reaction following intramuscular injection in some horses. This may constitute drug sensitivity and should result in discontinuation of therapy until or unless another cause is determined.

None known. It is recommended that the horse have close veterinary observation if other drugs are being given during the treatment period to ensure that they are compatible. NSAID toxicities are additive and NSAIDs should not be used in combination.

Safety unknown.

No adverse effects on spermatogenesis (production of sperm).

Detection Time Information: Flunixin’s pharmacological effects are not thought of as lasting longer than 24 hours after a clinical dose, and they may last slightly less, particularly after an IV dose. Flunixin clears the blood and urine rapidly (24-48 hours) if detection is less sensitive, but if detection is highly sensitive, flunixin can be detected in urine for up to 2 weeks after a course of therapy. Canadian and Australian researchers report a detection time of 3 days in horses, while 2 days is likely a more consistent figure in the United States. There is no ARCI-recommended plasma-level threshold or tolerance level for flunixin, but California officially permits a level of up to 1.0 mcg/ml in the blood, while Pennsylvania permits a level of up to 0.1 mcg/ml.


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