Hydrochlorothiazide (HCT) is an antihypertensive thiazide diuretic that is used to treat hypertension and chronic kidney disease. HCT competes for the Cl- site on the Na+/Cl- co-transporter (NCCT), decreasing reabsorption of Na+ in the distal convoluted tubule, inducing natriuresis and decreasing blood volume. HCT also partially inhibits carbonic anhydrase I in erythrocytes and vascular smooth muscle cells; this mechanism may be behind the ability of HCT to decrease peripheral vascular resistance and blood pressure. Separately, HCT may also increase reabsorption of Ca2+. This compound may also exhibit anticancer chemotherapeutic benefit in conjunction with UVA light, as it enhances production of TT dimers in vitro and in vivo.