Hydrochlorothiazide directly inhibits the sodium chloride cotransporter located on the apical membrane of the distal convoluted tubules in the kidney. Hydrochlorothiazide affects the distal renal tubular mechanism of electrolyte reabsorption. At maximal therapeutic dosage all thiazides are approximately equal in their diuretic efficacy. Hydrochlorothiazide increases excretion of sodium and chloride in approximately equivalent amounts.