How does this medication work? What will it do for me?

Metolazone belongs to the class of medications called diuretics. It is used to treat blood pressure and to remove excessive water (edema) that occurs in such conditions as congestive heart failure and some forms of kidney disease.

It usually takes 3 to 4 days for metolazone to start reducing edema, and 3 to 6 weeks to start reducing blood pressure.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each pink, slightly biconvex tablet, debossed with its numeric strength on one side and "ZAROXOLYN" on the other, contains metolazone 2.5 mg. Nonmedicinal ingredients: microcrystalline cellulose, D&C Red No. 33 Aluminum Lake, and magnesium stearate. This medication does not contain alcohol, gluten, lactose, paraben, sucrose, or tartrazine.

How should I use this medication?

The recommended dose of metolazone ranges from 2.5 mg to 20 mg daily depending on the condition being treated and the circumstances of the person taking the medication. For treatment of high blood pressure, the usual dose is 2.5 mg to 5 mg once daily. For treatment of edema, the usual dose ranges from 5 to 20 mg once daily.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to metolazone or any ingredients of this medication
  • are unable to urinate

Do not give this medication to people who are in hepatic coma or pre-coma.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • decreased sexual ability
  • diarrhea
  • dizziness or lightheadedness when getting up from a lying or sitting position
  • increased sensitivity of skin to sunlight
  • loss of appetite
  • upset stomach

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • cough or hoarseness
  • fever or chills
  • joint pain
  • lower back or side pain
  • painful or difficult urination
  • pinpoint-sized red spots on skin
  • skin rash or hives
  • stomach pain (severe) with nausea and vomiting
  • signs and symptoms of too much potassium loss:
    • dryness of mouth
    • increased thirst
    • irregular heartbeat
    • mood or mental changes
    • muscle cramps or pain
    • nausea or vomiting
    • unusual tiredness or weakness
    • weak pulse
  • signs and symptoms of too much sodium loss:
    • confusion
    • convulsions
    • decreased mental activity
    • irritability
    • muscle cramps
    • unusual tiredness or weakness
  • yellow eyes or skin

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Diabetes: If you have diabetes, your doctor should closely monitor your condition while you are taking metolazone, as it may affect blood sugar control (by increasing blood sugar levels).

Electrolytes: Metolazone may cause imbalances of electrolytes in the blood such as potassium, sodium, and magnesium. The signs of electrolyte imbalance include:

  • drowsiness
  • dry mouth
  • lethargy
  • low blood pressure
  • muscle fatigue
  • muscle pains or cramps
  • racing heart rate
  • reduced urine output
  • restlessness
  • stomach disturbances such as nausea and vomiting
  • thirst
  • weakness

If you have these symptoms, contact your doctor as soon as possible.

Gout: High blood uric acid levels may be brought on by metolazone. This may result in a gout attack for people with a history of gout. If you have a history of gout, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney and liver function: If you have reduced kidney or liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking metolazone, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

What other drugs could interact with this medication?

There may be an interaction between metolazone and any of the following:

  • alcohol
  • barbiturates (e.g., phenobarbital)
  • cholestyramine
  • colestipol
  • corticosteroids (e.g., prednisone)
  • diabetes medications (e.g., insulin, glyburide, metformin)
  • diazoxide
  • digoxin
  • furosemide
  • gout medications (e.g., colchicine)
  • lithium
  • medications that lower blood pressure (e.g., hydrochlorothiazide, ramipril)
  • methenamine
  • narcotics (e.g., codeine, morphine)
  • nonsteroidal anti-inflammatory medications (NSAIDs; e.g., ibuprofen, naproxen)
  • salicylates (e.g., acetylsalicylic acid [ASA])
  • sympathomimetic medications (e.g., pseudoephedrine, phenylephrine, dopamine, epinephrine, dobutamine)
  • tubocurarine

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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