Suxibuzone is an analgesic used for joint and muscular pain. It is a prodrug of the nonsteroidal anti-inflammatory drug (NSAID) phenylbutazone, and is commonly used in horses. Suxibuzone is an analgesic used for joint and muscular pain. It is a prodrug of the nonsteroidal anti-inflammatory drug (NSAID) phenylbutazone, and is commonly used in horses.