Buy Zytanix 2.5 mg (Metolazone), Metolazone is a thiazide diuretic (water pill) that helps prevent your body from absorbing too much salt, which can cause fluid retention. Metolazone treats fluid retention (edema) in people with congestive heart failure or a kidney disorder such as nephrotic syndrome. This medication is also used to treat high blood pressure hypertension). Zaroxolyn is another trade name for Metolazone.