Phenylbutazone (“bute”) is an anti-inflammatory drug—a non-steroidal anti-inflammatory similar to aspirin, Advil, Motrin, Banamine, etc. Bute has been used for decades in horses to relieve pain, particularly in musculoskeletal injuries, navicular syndrome, arthritis, and so on. Melinda Freckleton, DVM (a private practitioner in Catlett, Virginia) says this is a drug that is used frequently and is a comparatively safe and effective way to reduce pain and inflammation.