Chlorthalidone is a thiazide-like diuretic used for the treatment of hypertension and for management of edema caused by conditions such as heart failure or renal impairment. Chlorthalidone improves blood pressure and swelling by preventing water absorption from the kidneys through inhibition of the Na+/Cl− symporter in the distal convoluted tubule cells in the kidney. The exact mechanism of chlorthalidone's anti-hypertensive effect is under debate, however, it is thought that increased diuresis results in decreased plasma and extracellular fluid volume, decreased cardiac output and therefore overall reduction in blood pressure. Chlorthalidone is considered first-line therapy for management of uncomplicated hypertension as there is strong evidence from meta-analyses that thiazide diuretics such as chlorthalidone reduce the risk of stroke, myocardial infarction, heart failure, and cardiovascular all-cause mortality in patients with hypertension. In particular, the ALLHAT trial confirmed the role of thiazide diuretics as first-line therapy and demonstrated that chlorthalidone had a statistically significant lower incidence of stroke and heart failure when compared to Lisinopril, Amlodipine, or Doxazosin. Further studies have indicated that low-dose thiazides are as good as, and in some secondary endpoints, better than β-blockers, ACE inhibitors, Calcium Channel Blockers or ARBs. Chlorthalidone has been shown to have a number of pleiotropic effects that differentiate it from other diuretics such as Hydrochlorothiazide. In addition to its antihypertensive effects, chlorthalidone has also been shown to decrease platelet aggregation and vascular permeability, as well as promote angiogenesis in vitro, which is thought to be partly the result of reductions in carbonic anhydrase–dependent pathways. These pathways may play a role in chlorthalidone's cardiovascular risk reduction effects.