Lasix (furosemide) vs. Zaroxolyn (metolazone)

• Lasix (furosemide) and Zaroxolyn (metolazone) are diuretics (water pills) used treat excess accumulation of fluid or swelling of the body (edema) and high blood pressure (hypertension).
• Lasix is a brand name for furosemide.
• Zaroxolyn is a brand name for metolazone.
• Side effects of Lasix and Zaroxolyn that are similar include electrolyte depletion, dizziness, nausea, abdominal pain, increased blood sugar, and increased uric acid levels.
• Side effects of Lasix that are different from Zaroxolyn include low blood pressure, dehydration, yellowing skin and eyes (jaundice), ringing in the ears, sensitivity to light, rash, pancreatitis, and diarrhea.
• Side effects of Zaroxolyn that are different from Lasix include high blood calcium, lightheadedness, headache, fatigue, vomiting, and constipation.

Lasix is a “loop” diuretic (water pill) used to eliminate water and salt from the body. Salt (composed of sodium and chloride), water, and other small molecules normally are filtered out of the blood by the kidneys and into the kidney tubules, which becomes urine. Most of the sodium, chloride, and water filtered out of the blood are reabsorbed into the blood before the filtered fluid becomes urine and is eliminated from the body. Lasix works by blocking the absorption of salt and water from the filtered fluid in the kidney tubules, causing a marked increase in urine output (diuresis).

Zaroxolyn 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, Zaroxolyn is chemically related to the thiazide class of diuretics (for example, chlorthalidone [Hygroton], hydrochlorothiazide), and works in a similar manner.

Lasix

Common side effects of Lasix are:

• Low blood pressure
• Dehydration
• Electrolyte depletion (for example, sodium, potassium)

Other important side effects include:

• Jaundice
• Ringing in the ears (tinnitus)
• Sensitivity to light (photophobia)
• Rash
• Pancreatitis
• Nausea
• Diarrhea
• Abdominal pain
• Dizziness

Increased blood sugar and uric acid levels also may occur.

Zaroxolyn

Zaroxolyn generally is well tolerated. Common side effects of Zaroxolyn are:

• Hypokalemia (low blood potassium)
• Hyponatremia (low blood sodium)
• Hypomagnesemia (low blood magnesium)
• Hypercalcemia (high blood calcium)

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
• Constipation

Thiazide diuretics, which are chemically related to Zaroxolyn, are known to increase the amount of uric acid in the blood. Precipitation of gout (which is associated with high uric acid) is rare. Zaroxolyn can increase blood sugar in people with diabetes.

Lasix

• The usual starting oral dose for treatment of edema in adults is 20 to 80 mg as a single dose. The same dose or an increased dose may be administered 6 to 8 hours later. Doses may be increased by 20 to 40 mg every 6 to 8 hours until the desired effect occurs. The effective dose may be administered once or twice daily. Some patients may require 600 mg daily.
• The starting oral dose for children is 2 mg/kg. The starting dose may be increased by 1 to 2 mg/kg every 6 hours until the desired effect is achieved. Doses greater than 6 mg/kg are not recommended.
• The recommended dose for treating hypertension is 40 mg twice daily. The dose of other blood pressure medications should be reduced by half when Lasix is added.

Zaroxolyn

• The recommended dose is 2.5 to 5 mg for hypertension and 2.5 to 20 mg for treating edema.

Lasix

• Administration of Lasix with aminoglycoside antibiotics (for example, gentamicin) or ethacrynic acid (Edecrin, another diuretic) may cause hearing damage.
• Lasix competes with aspirin for elimination in the urine by the kidneys. Concomitant use of Lasix and aspirin may, therefore, lead to high blood levels of aspirin and aspirin toxicity.
• Lasix also may reduce excretion of lithium (Eskalith, Lithobid) by the kidneys, causing increased blood levels of lithium and possible side effects from lithium.
• Sucralfate (Carafate) reduces the action of Lasix by binding Lasix in the intestine and preventing its absorption into the body. Ingestion of Lasix and sucralfate should be separated by two hours.
• When combined with other antihypertensive drugs, there is an increased risk of low blood pressure or reduced kidney function.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) -- for example, ibuprofen, indomethacin (Indocin, Indocin-SR) -- may interfere with the blood pressure reducing effect of Lasix.

Zaroxolyn

• Zaroxolyn can reduce blood potassium and magnesium levels. This is especially true in patients who also are taking "loop" diuretics such as Lasix (furosemide), Bumex (bumetanide), and Demadex (torsemide). Low potassium and magnesium levels can lead to heart rhythm abnormalities, especially in patients taking Lanoxin (digoxin).
• Zaroxolyn 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 Zaroxolyn by interfering with the excretion of salt and water.

Lasix

• Lasix is secreted in breast milk. Nursing mothers should avoid breastfeeding while taking Lasix.

Zaroxolyn

• Zaroxolyn should not be used during pregnancy unless absolutely necessary.
• Zaroxolyn is excreted in breast milk. Intense diuresis during Zaroxolyn use may reduce the production of milk. Otherwise, Zaroxolyn is considered safe to use during nursing if required by the mother.