A drug or other agent that increases the rate of urine formation and hence the rate at which water and certain salts are lost from the body. Many diuretic drugs work by decreasing the reabsorption of sodium and chloride ions from the filtrate in the kidney tubules, so that less water is reabsorbed. They are used to treat fluid retention (oedema) arising from disorders of the heart, kidneys, or other organs, and are used in helping to reduce high blood pressure (hypertension). There are several groups of diuretic drugs, with different modes of action. The most powerful are loop diuretics, such as furosemide, which act primarily by blocking Na⁺/K⁺/Cl⁻ carriers in cells of the loop of Henle. Another group consists of the thiazides, such as metolazone, which inhibit Na⁺/Cl⁻ transport in the distal convoluted tubule. Spironolactone exerts its diuretic effect by blocking the binding of the hormone aldosterone to its receptors. The osmotic diuretics, such as mannitol, act by increasing the osmolarity of the filtrate, and hence increasing urine volume.