Torsemide (AC-4464) is an anilinopyridine sulfonylurea belonging to the class of loop diuretics. Torsemide has a prolonged duration of action compared to other loop diuretics, is extensively protein bound in plasma and has a relatively long half-life.

In rats, compared to baseline levels, Torsemide increases blood urea nitrogen (BUN) and plasma creatinine concentrations, and significantly and rapidly augments urine output. In canines with mitral valve closure, Torsemide elevates circulating angiotensin II and aldosterone levels, whereas furosemide only increases the level of angiotensin II.

The primary action site of Torsemide is the thick ascending limb of the loop of Henle, where it promotes the excretion of water, sodium, and chloride by interacting with the K+, Na+, Cl- transporter. Torsemide disrupts the binding and secretion of aldosterone in a dose-dependent manner. It inhibits aldosterone secretion, which is produced by adrenal cortical cells of mice, guinea pigs, and cattle, and is stimulated in vivo by angiotensin, adrenocorticotropic hormone, butyryl cyclic AMP, corticosterone, or in vitro.