One of the earliest NSAID approved for use in horses and dogs, phenylbutazone is a pyrazolone derivative available in tablet, paste, gel, and parenteral formulations.

Once absorbed, binding to plasma proteins is high (99% in horses, 93% in cattle). Phenylbutazone is metabolized by the liver to several active (oxyphenbutazone) and inactive metabolites, which are excreted in urine.