A group of moderately potent DIURETICS which are effective when taken by mouth. They act by inhibiting the reabsorption of sodium and chloride in the renal tubules. They also have a blood-pressure-lowering effect but their main use is to relieve OEDEMA in heart failure.

All thiazides are active by mouth, with most having an onset of action within 1–2 hours, and duration of 12–24 hours. They include bendrofluazide, cyclopenthiazide, hydrochlorothiazide, hydroflumethiazide, indapamide, mefruside, methychlothiazide, metolazone, polythiazide and xipamide.