Bute, Firocoxib Compared for Alleviating Hoof Lameness

Bute, Firocoxib Compared for Alleviating Hoof Lameness

Bute was more effective than firocoxib at alleviating hoof pain at label dose, but Foreman noted that new dosing recommendations for the latter drug could change those results.

Photo: Alexandra Beckstett, The Horse Managing Editor

The non-steroidal anti-inflammatory drug (NSAID) firocoxib hit the market in 2007 and has since gained popularity due to its propensity to cause fewer side effects than its counterpart, phenylbutazone (commonly known as Bute, or PBZ). But how do the two compare at alleviating lameness in horses?

A research team from the University of Illinois recently set out to answer that question, and shared their findings at the 2014 International Conference on Equine Exercise Physiology, held June 16-20 in Chester, U.K.

Non-steroidal anti-inflammatory drugs target the enzyme cyclooxygenase (COX), which is responsible for the body's inflammatory responses. There are two "subtypes" of COX: COX-2 is primarily associated with inflammation, while COX-1 is associated with normal day-to-day processes such as protecting the gastric mucosa (lining). While traditional NSAIDs, like PBZ, block both COX-1 and -2, some newer ones—like firocoxib—are designed to target the inflammation associated with COX-2 while sparing the COX-1 enzymes.

Jonathan H. Foreman, DVM, MS, Dipl. ACVIM, professor of veterinary clinical medicine at the school's College of Veterinary Medicine Veterinary Teaching Hospital, and colleagues set out to test their hypothesis that intravenous (IV) firocoxib at label dose and PBZ had comparable efficacies and that both would be effective in alleviating lameness caused by foot pain.

The researchers induced reversible lameness in eight healthy adult horses by using an adjustable heart bar shoe that could be tightened with a screw to elicit lameness ranging from mild to severe. An hour after lameness induction the team administered one of the following treatments to each horse:

  • 1 ml (milliliter)/45 kg (kilograms) body weight of saline (to serve as untreated controls);
  • 4.4 mg (milligrams)/kg of PBZ; or
  • 0.09 mg/kg (the label dose) of firocoxib.

A blinded investigator monitored horses' heart rates and lameness scores every 20 minutes for five hours after lameness induction and continued monitoring them hourly through 12 hours after treatment. The team repeated the experiment one and two weeks later, shuffling the treatment groups.

Foreman and colleagues found that horses' post-treatment heart rates and lameness scores were lower in PZB-treated horses than in firocoxib- and saline-treated horses at varying time points. Additionally, they found no difference between firocoxib- and saline-treated horses' heart rates and lameness scores.

But there's one important key to consider with regard to these results, Foreman said: "The manufacturer now recommends that the first intravenous dose be three times (3x) the label dose, essentially a loading dose which should provide much quicker effect than the 1x label dose which takes three to five days to reach steady state and peak effect. Then following that, once a day with the label dose (1x) should provide good effect with IV firocoxib."

Foreman said he and colleagues recently tested the 3x protocol, and the results look much better with the loading dose than with the label dose for the first dose.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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