Hydrochlorothiazide (HCT). Molecular model of hydrochlorothiazide (C7.H8.Cl.N3.O4.S2). This is a diuretic medication available as a generic drug. It is used for the treatment of hypertension, congestive heart failure, symptomatic edema, diabetes insipidus, and renal tubular acidosis. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red), chlorine (green) and sulfur (yellow).