Generic name: metolazone (me TOL a zone)
Brand name: Zaroxolyn
Drug class: Thiazide diuretics

Zaroxolyn is a thiazide diuretic (water pill) that helps prevent your body from absorbing too much salt, which can cause fluid retention.

Zaroxolyn is used to treat fluid retention (edema) in people with congestive heart failure, or a kidney disorder such as nephrotic syndrome. This medicine is also used to treat high blood pressure (hypertension).

Zaroxolyn may also be used for purposes not listed in this medication guide.


You should not use Zaroxolyn if you are unable to urinate, or if you have severe liver disease.

What should I discuss with my doctor before taking Zaroxolyn?

You should not use Zaroxolyn if you are allergic to it, or if you have:

  • severe liver disease; or
  • if you are unable to urinate.

To make sure Zaroxolyn is safe for you, tell your doctor if you have:

  • an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);
  • a heart rhythm disorder;
  • an allergy to sulfa drugs;
  • liver disease;
  • kidney disease;
  • diabetes;
  • gout; or
  • systemic lupus erythematosus.

Using Zaroxolyn during pregnancy could cause side effects in the newborn baby, such as blood cell problems, or jaundice (yellowing of the skin or eyes). Tell your doctor if you are pregnant or if you become pregnant while using Zaroxolyn.

Metolazone can pass into breast milk and may harm a nursing baby. You should not breast-feed while using this medicine.

Zaroxolyn is not approved for use by anyone younger than 18 years old.

How should I take Zaroxolyn?

Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Zaroxolyn is usually taken only once per day.

You may need to limit salt in your diet while taking this medicine. Follow your doctor's instructions carefully.

While using Zaroxolyn, you may need frequent blood tests. Your blood and urine may both be tested if you have been vomiting or are dehydrated.

Zaroxolyn can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using this medicine.

If you need surgery, tell the surgeon ahead of time that you are using Zaroxolyn. You may need to stop using the medicine for a short time.

If you are being treated for high blood pressure, keep using this medicine even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medicine for the rest of your life.

Store the tablets at room temperature away from heat, light, and moisture.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include severe dizziness or drowsiness, dry mouth, thirst, muscle weakness, feeling light-headed, or fainting.

What should I avoid while taking Zaroxolyn?

Drinking alcohol with Zaroxolyn can cause side effects.

Avoid becoming overheated or dehydrated during exercise, in hot weather, or by not drinking enough fluids. Follow your doctor's instructions about the type and amount of liquids you should drink. In some cases, drinking too much liquid can be as unsafe as not drinking enough.

Zaroxolyn side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • chest pain;
  • pounding heartbeats or fluttering in your chest;
  • easy bruising or bleeding;
  • a light-headed feeling, like you might pass out;
  • liver problems--nausea, upper stomach pain, itching, tiredness, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
  • low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling;
  • low levels of sodium in the body--headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
  • other signs of an electrolyte imbalance--dry mouth, nausea, vomiting, weakness, drowsiness, lack of energy, muscle pain, little or no urination, or feeling restless; or
  • severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common side effects may include:

  • dizziness, spinning sensation;
  • drowsiness, tiredness;
  • depressed mood;
  • muscle or joint pain;
  • numbness or tingly feeling;
  • nausea, stomach pain, loss of appetite; or
  • diarrhea, constipation.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Zaroxolyn?

Taking Zaroxolyn with other drugs that make you make you light-headed can worsen this effect. Ask your doctor before taking Zaroxolyn with a narcotic pain medicine, muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your current medicines and any you start or stop using, especially:

  • any other blood pressure medication;
  • digoxin, digitalis;
  • furosemide or other diuretics (water pills);
  • insulin or oral diabetes medicine;
  • lithium;
  • methenamine;
  • vitamin D (at high doses);
  • a blood thinner--warfarin, Coumadin, Jantoven;
  • NSAIDs (nonsteroidal anti-inflammatory drugs)--ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib, diclofenac, indomethacin, meloxicam, and others;
  • salicylates--aspirin, Nuprin Backache Caplet, Kaopectate, KneeRelief, Pamprin Cramp Formula, Pepto-Bismol, Tricosal, Trilisate, and others; or
  • steroid medicine--prednisone and others.

This list is not complete. Other drugs may interact with metolazone, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.