Diclofenac sodium is the sodium salt of diclofenac, a nonsteroidal anti-inflammatory drug (NSAID) and phenylacetic acid derivative widely used as an active pharmaceutical ingredient (API) in the formulation of medications. It is employed to alleviate pain, reduce inflammation, and manage fever in treatments for conditions such as osteoarthritis, rheumatoid arthritis, acute injuries, dental pain, postoperative recovery, migraines, and menstrual cramps. Available in oral, topical (gel or patch), and injectable forms in finished products, it requires careful handling in manufacturing due to potential side effects on the gastrointestinal tract, kidneys, and cardiovascular system when used therapeutically. As a reagent, it appears as a white to off-white powder, with purity typically 98.5-101.5%, and is soluble in water (50 mg/mL, clear solution).