Metolazone (MTZ)

Metolazone is primarily used to treat congestive heart failure and high blood pressure. Metolazone indirectly decreases the amount of water reabsorbed into the bloodstream by the kidney, so that blood volume decreases and urine volume increases. This lowers blood pressure and prevents excess fluid accumulation in heart failure. Metolazone is sometimes used together with loop diuretics such as furosemide or bumetanide, but these highly effective combinations can lead to dehydration and electrolyte abnormalities. Metolazone is a quinazoline, a derivative of the similar diuretic quinethazone, as well as a sulfonamide. It is related to analogs of 1,2,4-benzothiadizine-1,1-dioxide (benzothiadiazine). These drugs are called benzothiadiazides, or thiazides for short. Chemically, metolazone is not a substituted benzothiadiazine, and therefore is not technically a thiazide.