Ethacrynic acid (CAS 58-54-8; C₁₃H₁₂Cl₂O₄) is a synthetic organic compound classified as a loop diuretic and specialty chemical used in pharmaceutical research and as an active pharmaceutical ingredient (API). It is primarily employed as a potent diuretic to manage conditions associated with fluid retention, such as edema caused by heart failure, kidney disorders, or liver disease. It works by inhibiting the reabsorption of sodium and chloride in the kidneys, promoting the excretion of excess fluid and reducing swelling. This compound is particularly useful in cases where other diuretics are ineffective or contraindicated, such as in patients with sulfa allergies. Additionally, it may be used in emergency situations to rapidly reduce fluid overload, such as in acute pulmonary edema. Due to its strong effects and potential for ototoxicity and electrolyte imbalances, it requires close medical supervision when used clinically.