Chlorthalidone is a thiazide-like diuretic, an inhibitor of the Na+-Cl- cotransporter. Chlorthalidone inhibits sodium ion transport across the renal tubular epithelium increasing the delivery of sodium to the distal renal tubule and indirectly increasing potassium excretion via the sodium-potassium exchange mechanism. Chlorthalidone also promotes Ca++ reabsorption by an unknown mechanism. Several recent comparison studies inidcate that chlorthalidone may be a better drug in preventing cardiovascular events than hydrochlorothiazide.