Many horse owners, breeders and trainers keep prescription drugs on hand in their tack boxes. One of the most common is bute (short for phenylbutazone). As with all drugs, prescription or non-prescription, it is important to understand the potential risks and benefits of this popular medication before giving it.
Bute is a powerful nonsteroidal anti-inflammatory drug – that is, it is in the same family of drugs as aspirin. It is used in horses instead of aspirin because of its long duration of effect – twelve hours compared to four to six for aspirin. It is effective against fever, swelling and inflammation from injuries and infections, laminitis (founder) and musculoskeletal pain. It is commonly used to relieve pain from chronic arthritis resulting from navicular disease, ringbone, bone spavin and similar conditions. It is not very effective for gastrointestinal pain (colic). Contrary to popular belief, it is not a mind-altering drug. It will not sedate a horse or make it “hyper.”
Bute is usually dispensed in one gram tablets. A moderate dose for a 1000 lb horse is one of these tablets every twelve hours, but the dose for an individual horse should always be determined by a veterinarian. The vast majority of healthy 1000 lb. horses can be maintained on the above dose for a long period of time (in some cases months or even years) without harmful effects. A rare horse will suffer side effects, however. These adverse effects usually involve the gastrointestinal system. Always contact your veterinarian right away if your horse shows any signs of gastrointestinal distress while on bute – colic, diarrhea, lack of appetite, or depression. These signs could signal impending ulceration of the stomach/and/or intestine, which can be very serious. Do not give bute for colic, since it is not effective for this condition and may limit the types of medications that your veterinarian can treat your horse with. Young horses, especially those under the age of two, are extremely susceptible to bute toxicity. Always consult a veterinarian before giving a young horse this medication. Recent studies have suggested that the addition of linoleic acid to the diet may help combat the gastrointestinal side effects. The addition of 1/4 cup of safflower or corn oil to the diet with each dose will accomplish this.
Call your veterinarian for advice before giving bute to a sick horse, or to one that is tied up. Sick horses are often dehydrated, and giving bute to a dehydrated horse can cause permanent kidney damage. In addition, take the horse’s temperature before giving bute – bute lowers body temperature, and your veterinarian may want to know whether or not the horse has a fever before you give it.