|AHFS/Drugs.com||International Drug Names|
|Chemical and physical data|
|Molar mass||296.24 g/mol|
|3D model (JSmol)|
Flunixin is a nonsteroidal anti-inflammatory drug (NSAID), analgesic, and antipyretic used in horses, cattle and pigs. It is often formulated as the meglumine salt. In the United States, it is regulated by the U.S. Food and Drug Administration (FDA), and may only be lawfully distributed by order of a licensed veterinarian. There are many trade names for the product.
Dosage and uses in horses
Flunixin is administered at a dose of 1.1 mg/kg. The full analgesic and antipyretic effects usually occur 1–2 hours following treatment, but there is often an effective analgesic effect within approximately 15 minutes. Despite its short plasma half life of 1.6-2.5 hours, effects can persist for up to 30 hours, with maximal effects occurring between 2 and 16 hours. This is likely due to accumulation of the drug at inflammatory foci. Flunixin is primarily eliminated by the kidneys.
Side effects and precautions
Flunixin is a prohibited substance under International Federation for Equestrian Sports rules, and its use is prohibited or restricted by many other equestrian organizations. At labeled dose (1.1 mg/kg) given IV, detection time was found to be 144 hours. However, drug recycling from bedding contamination by treated horses has been shown to potentially increase the clearance time.
Flunixin may be given orally as a paste or as granules in feed. It can also be used intramuscularly (IM) or intravenously (IV). However, it is very irritating to tissue and IM administration has been associated with myonecrosis in horses, so IV administration is preferred.
Administration of phenylbutazone to a horse also receiving flunixin has been shown to increase the risk of toxicity without improving analgesia. For this reason, concurrent administration with another NSAID is not recommended. Doubling the dose of flunixin produces no improvement in analgesia, while potentially increasing the risk of toxicity.
In the US, the only labeled route for flunixin administration in cattle is intravenous. This is not the case in other countries; for example, in the UK, Allevenix is licensed for IV and intramuscular use, and a pour-on product also exists.
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