Clinical data
AHFS/Drugs.com International Drug Names
ATCvet code QM01AG90 (WHO)
CAS Number 38677-85-9 YesY
PubChem (CID) 38081
ChemSpider 34911 N
UNII 356IB1O400 YesY
KEGG D04215 YesY
ECHA InfoCard 100.115.991
Chemical and physical data
Formula C14H11F3N2O2
Molar mass 296.24 g/mol
3D model (Jmol) Interactive image
 NYesY (what is this?)  (verify)

Flunixin is a non-steroidal 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.[1] 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,[2] 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.[3]

Because it targets the inflamed tissue, flunixin is mainly used for colic pain, musculoskeletal pain, and ocular pain.[4][5][6] It is also used as an antipyretic and to reduce the effects of endotoxemia.[7]

Side effects and precautions

Flunixin is labeled for no more than 5 days of consecutive use and prolonged use increases the risk of toxicity. In horses, this includes gastric ulcers,[8] right dorsal colitis,[9] and nephrotoxicity.[10]

Flunixin is a prohibited substance under International Federation for Equestrian Sports rules,[11] 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.[12] However, drug recycling from bedding contamination by treated horses has been shown to potentially increase the clearance time.[13]


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,[14] 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.[15][16] 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.[4]

In cattle, the only labeled route for flunixin administration is intravenous.

See also


  1. McIlwraith CW, Frisbie DD, Kawcak CE. Nonsteroidal Anti-Inflammatory Drugs. Proc. AAEP 2001 (47): 182-187.
  2. May SA, Lees P. Nonsteroidal anti-inflammatory drugs. In McIlwraith CW, Trotter GW, eds. Joint disease in the horse. Philadelphia: WB Saunders, 1996;223–237.
  3. Soma, L R (11/01/1988). "Disposition and excretion of flunixin meglumine in horses". American journal of veterinary research (0002-9645), 49 (11), p. 1894.
  4. 1 2 Foreman, J. H., Bergstrom, B. E., Golden, K. S., Roark, J. J., Coren, D. S., Foreman, C. R. and Schumacher, S. A. (2012), Dose titration of the clinical efficacy of intravenously administered flunixin meglumine in a reversible model of equine foot lameness. Equine Veterinary Journal, 44: 17–20. doi: 10.1111/j.2042-3306.2012.00655.x
  5. JOCHLE, W., MOORE, J. N., BROWN, J., BAKER, G. J., LOWE, J. E., FUBINI, S., REEVES, M. J., WATKINS, J. P. and WHITE, N. A. (1989), Comparison of detomidine, butorphanol, flunixin meglumine and xylazine in clinical cases of equine colic. Equine Veterinary Journal, 21: 111–116. doi: 10.1111/j.2042-3306.1989.tb05668.x
  6. Hilton, H.G., Magdesian, K.G., Groth, A.D., Knych, H., Stanley, S.D. and Hollingsworth, S.R. (2011), Distribution of Flunixin Meglumine and Firocoxib into Aqueous Humor of Horses. Journal of Veterinary Internal Medicine, 25: 1127–1133. doi: 10.1111/j.1939-1676.2011.0763.x
  7. Bryant, C.E., Farnfield, B.A. & Janicke, H.J. (2003) Evaluation of theability of carprofen and flunixin meglumine to inhibit activation ofnuclear factor kappa B. American Journal of Veterinary Research, 64,211–215.
  8. Videla, R. & Andrews, F.M. (2009) New perspectives in equine gastriculcer syndrome. The Veterinary Clinics of North America. Equine Practice, 25, 283–301.
  9. McConnico, R.S., Morgan, T.W., Williams, C.C., Hubert, J.D. & Moore,R.M. (2008) Pathophysiologic effects of phenylbutazone on the rightdorsal colon in horses. American Journal of Veterinary Research, 69,1496–1505.
  10. Black, H.E. (1986) Renal toxicity of non-steroidal anti-inflammatory drugs. Toxicologic Pathology, 14,83–90.
  11. "FEI Prohibited Substances List". Retrieved 23 January 2016.
  12. "FEI List of Detection Times" (PDF). Retrieved 23 January 2016.
  13. POPOT, M. A., GARCIA, P. and BONNAIRE, Y. (2011), Doping control in horses: housing conditions and oral recycling of flunixin by ingestion of contaminated straw. Journal of Veterinary Pharmacology and Therapeutics, 34: 612–614. doi: 10.1111/j.1365-2885.2011.01276.x
  14. Peek SF, Semrad SD, Perkins GA. Clostridial myonecrosis in horses (37 cases 1985–2000). Equine Vet J 2003;35:86–92
  15. FOREMAN, J. H. and RUEMMLER, R. (2011), Phenylbutazone and flunixin meglumine used singly or in combination in experimental lameness in horses. Equine Veterinary Journal, 43: 12–17. doi: 10.1111/j.2042-3306.2011.00485.x
  16. Reed, S.K., Messer, N.T., Tessman, R.K. and Keegan, K.G. (2006) Effects of phenylbutazone alone or in combination with flunixin meglumine on blood protein concentrations in horses. Am. J. vet. Res. 67, 398-402.
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