Firocoxib-d4 is the deuterated form of firocoxib, a non-steroidal anti-inflammatory drug (NSAID) used primarily in veterinary medicine for managing pain and inflammation in animals, particularly dogs and horses. Conditions treated include osteoarthritis, post-surgical pain, and musculoskeletal disorders. As an internal standard in analytical chemistry, firocoxib-d4 aids in the precise quantification of firocoxib in biological samples using techniques like liquid chromatography-mass spectrometry (LC-MS). This supports accurate pharmacokinetic studies, drug metabolism analysis, and quality control in pharmaceutical development.