metolazone, Zaroxolyn, Diulo (Discontinued); Mykrox (Discontinued)

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GENERIC NAME: metolazone

BRAND NAME: Zaroxolyn, Diulo (Discontinued), Mykrox (Discontinued)

DRUG CLASS AND MECHANISM: Metolazone is a diuretic ("water pill") used in the treatment of high blood pressure and fluid accumulation. It works by blocking salt and fluid retention by the kidneys, thereby increasing urinary output of salt and water (diuresis). Although it is not a true thiazide, metolazone is chemically related to the thiazide class of diuretics (for example, chlorthalidone [Hygroton], hydrochlorothiazide), and works in a similar manner. Zaroxolyn is the original formulation of metolazone, and Diulo is similar. The absorption of these two drugs is relatively incomplete. Mykrox has more complete absorption. Therefore, less Mykrox needs to be given to have the same effects as a larger dose of Zaroxolyn or Diulo. Metolazone was approved by the FDA in 1973.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Tablets: 2.5, 5, and 10 mg.

STORAGE: Tablets should be stored at room temperature, 15-30 C (59-86 F).

PRESCRIBED FOR: Metolazone is used in the treatment of high blood pressure and edema (fluid retention).

DOSING: The recommended dose is 2.5 to 5 mg for hypertension and 2.5-20 mg for treating edema.

DRUG INTERACTIONS: Metolazone can reduce blood potassium and magnesium levels. This is especially true in patients who also are taking "loop" diuretics such as furosemide (Lasix), bumetanide (Bumex), and torsemide (Demadex ). Low potassium and magnesium levels can lead to heart rhythm abnormalities, especially in patients taking digoxin (Lanoxin). Metolazone reduces excretion of lithium (Lithobid, Eskalith) by the kidneys and can lead to lithium toxicity in patients receiving lithium. Steroids (for example, hydrocortisone) and nonsteroidal anti-inflammatory agents (NSAIDs) such as ibuprofen (Motrin), naproxen (Naprosyn), and nabumetone (Relafen) can reduce the effectiveness of metolazone by interfering with the excretion of salt and water.

PREGNANCY: Metolazone should not be used during pregnancy unless absolutely necessary.

NURSING MOTHERS: Metolazone is excreted in breast-milk. Intense diuresis using metolazone may reduce the production of milk. Otherwise metolazone is considered safe to use during nursing if required by the mother.

SIDE EFFECTS: Metolazone generally is well tolerated. Hypokalemia (low blood potassium), hyponatremia (low blood sodium), and hypomagnesemia (low blood magnesium) are common side effects of metolazone. Hypercalcemia (high blood calcium) also may occur.

About 1 out of every 10 patients report dizziness, lightheadedness, and headache. Fatigue has been reported in 1 out of every 25 patients. About 1 out of every 50 patients reports nausea, vomiting, abdominal pain, or constipation. Thiazide diuretics, which are chemically related to metolazone, are known to increase the amount of uric acid in the blood. Precipitation of gout (which is associated with high uric acid) is rare. Metolazone can increase blood sugar in people with diabetes.

Reference: FDA Prescribing Information


Last Editorial Review: 4/6/2012




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