Study: Heavy Bute Use May Cause More Harm Than Good

Chronic use of phenylbutazone, or Bute, in horses with joint problems could be causing more problems than it's preventing. A recent study has shown that Bute and other non-steroidal anti-inflammatory medications (NSAIDS) might be detrimental to joint cartilage regeneration in horses.

The study was performed by Lisa Beluche, DVM; Alicia Bertone, DVM, PhD, Dipl. ACVS; David Anderson, DVM; and Carsten Rohde, DVM; of The Ohio State University's (OSU) Orthopedic Research Laboratory, and appeared in a recent issue of the American Journal of Veterinary Research. Eleven sound and radiographically normal 18- to 30-month-old horses were used in the study.

"The results are not that surprising, actually, that drugs which suppress inflammation might also slow healing," said Bertone, who is the new Trueman Family Endowed Chair in Equine Clinical Medicine and Surgery at OSU. She explained that some degree of inflammation is an important part of the healing process--a part that Bute or any NSAID could conceivably hinder. An OSU study published in May of 2000 reported that Bute suppressed bone formation and healing, and a previous human study showed that abdominal incisions were slower to heal when patients were treated with anti-inflammatory drugs.

The scientists in the current study state that "oral administration of phenylbutazone for 14 days significantly decreased proteoglycan synthesis (formation of one of the building blocks of cartilage) in articular culture explants from healthy horses to a degree similar to that induced by in vitro exposure to interleukin." Interleukin is one of the many mediators of inflammation, which stimulates chondrocytes (cartilage cells) to release proteins that inhibit proteoglycan synthesis and facilitate degeneration of proteoglycans.

Additionally, joint explants that were incubated with interleukin (from horses treated with Bute) showed no further decrease in cartilage production.

"These effectsÄare small, but measurable, and other NSAIDS probably have the same effects on cartilage," said Bertone. Bute or any other NSAID should be used in arthritic or painful horses only when needed to make the horse comfortable. She explained that in years past, the veterinary community used Bute "like it was water," in large quantities for long periods of time, but in recent years veterinarians have begun reducing dosages to the lowest possible levels to minimize the animal's pain.

Bertone stresses that pain relief is extremely important in the laminitic horse. These horses and horses with chronic osteoarthritis will need a minimal does of Bute or another NSAID to make them pasture sound. This allows the horse to use the joint more than he would with pain--mobility is known to help a horse recover. There is no evidence that lifelong use of Bute would cripple a horse.

The researchers' findings will drive the industry to develop painkillers that do not further harm the horse's systems, and Bertone explained that NSAIDs that address the pain of the horse with less of the side effects described in this study are currently in clinical trials. These drugs will be similar to human drugs on the market like celecoxib (Celebrex) and rofecoxib (Vioxx). (See for more on inflammation and NSAIDS.)

"The take-home message is that Bute is not an innocuous drug," she explained, "and horses that don't need it shouldn't be on it."