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Acetazolamide ("water pill", diuretic)

Written by Stephanie Nera, RPh, PharmD · Pharmacology

Updated Jun 30, 2021

Acetazolamide is a carbonic anhydrase inhibitor and “water pill” (diuretic). It decreases the amount of fluid that can build up in the eye. It is also used to decrease a buildup of body fluids (edema) caused by congestive heart failure or certain medications.


Know the basics

What is acetazolamide used for?

Acetazolamide is used to prevent and reduce the symptoms of altitude sickness. This medication can decrease headache, tiredness, nausea, dizziness, and shortness of breath that can occur when you climb quickly to high altitudes (generally above 10,000 feet/3,048 meters). It is particularly useful in situations when you cannot make a slow ascent. The best ways to prevent altitude sickness are climbing slowly, stopping for 24 hours during the climb to allow the body to adjust to the new height, and taking it easy the first 1 to 2 days.

This drug is also used with other medications to treat a certain type of eye problem (open-angle glaucoma). It may also be used to treat periodic paralysis.

How should I take acetazolamide?

If you are taking the tablets, take this medication by mouth, usually 1 to 4 times daily or as directed by your doctor. If you are taking the long-acting capsules, take this medication by mouth, usually 1 or 2 times daily or as directed by your doctor. Swallow the long-acting capsules whole. Do not open, break, or chew the capsules. Doing so can destroy the long action of the drug and may increase side effects.

Acetazolamide may be taken with or without food. Drink plenty of fluids unless otherwise directed by your doctor. Your dosage is based on your medical condition and response to therapy.

To prevent altitude sickness, start taking acetazolamide 1 to 2 days before you start to climb. Continue taking it while you are climbing and for at least 48 hours after you have reached your final altitude. You may need to continue taking this medication while staying at the high altitude to control your symptoms. If you develop severe altitude sickness, it is important that you climb down as quickly as possible. Acetazolamide will not protect you from the serious effects of severe altitude sickness. (See also Precautions.)

If you are taking this drug for another condition (e.g., glaucoma, seizures), use this medication regularly as directed to get the most benefit from it. To help you remember, take it at the same time(s) each day. Taking your last dose in the early evening will help prevent you from having to get up in the middle of the night to urinate. Consult your doctor or pharmacist if you have questions about your dosing schedule.

Do not increase or decrease your dose or stop using this medication without first consulting your doctor. Some conditions may become worse when this drug is suddenly stopped. Your dose may need to be gradually decreased.

When used for an extended period, this medication may not work as well and may require different dosing. Your doctor will be monitoring your condition. Tell your doctor if your condition does not improve or if it worsens (e.g., more frequent seizures).

This drug may reduce the potassium levels in your blood. Your doctor may recommend that you eat foods rich in potassium (e.g., bananas or orange juice) while you are taking this medication. Your doctor may also prescribe a potassium supplement for you to take during treatment. Consult your doctor for more information.

How do I store acetazolamide?

This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer. 

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using acetazolamide?

Before using this drug, tell your doctor if you are/have:

  • Pregnant or breastfeeding.
  • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
  • An allergy to any of the ingredients of this product.
  • Any other illnesses, disorders, or medical conditions.

Is it safe to take acetazolamide during pregnancy or breast-feeding?

Unfortunately, there isn’t enough information about the safety of using this drug during pregnancy and breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking any medication.

This medication is pregnancy risk category C according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Know the side effects

What are the side effects of acetazolamide?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

  • Blurred vision
  • Changes in taste
  • Constipation
  • Diarrhea
  • Drowsiness
  • Frequent urination
  • Loss of appetite
  • Nausea; vomiting
  • Seek medical attention right away if any of these severe side effects occur:

    • Severe allergic reactions: rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue
    • Blood in urine
    • Changes in hearing
    • Convulsions
    • Dark, bloody stools
    • Dark urine
    • Fast breathing
    • Fever
    • Lack of energy
    • Lower back pain
    • Red, swollen, or blistered skin
    • Ringing in the ears
    • Sore throat
    • Tingling of the arms or legs
    • Unusual bleeding or bruising
    • Vision changes
    • Yellowing of the skin or eyes

    However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.

    Know the interactions

    What drugs may interact with acetazolamide?

    This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. 

    To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. 

    Drugs with known interactions:

    • Aspirin
    • Arsenic Trioxide
    • Carbamazepine
    • Ceritinib
    • Dabrafenib
    • Digitalis
    • Droperidol
    • Metformin
    • Mitotane
    • Nilotinib
    • Quinidine
    • Sotalol

    If you experience an adverse drug interaction, inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

    Does food or alcohol interact with acetazolamide?

    This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Avoid drinking alcohol while taking this drug. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

    What health conditions may interact with acetazolamide?

    This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

    • Type 2 diabetes mellitus
    • Emphysema or other chronic lung disease
    • Low blood levels of potassium or sodium
    • Kidney disease or stones
    • Liver disease
    • Underactive adrenal gland (Addison’s disease)

    Understand the dosage

    The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

    What is the dose for an adult?


    • 250 to 375 mg oral or intravenous once a day.

    When continued acetazolamide therapy for edema is desired, it is recommended that every second or third dose be skipped to allow the kidney to recover.

    Acute Mountain Sickness

    • Oral tablet: 125 to 250 mg orally every 6 to 12 hours.
    • SR capsule: 500 mg orally every 12 to 24 hours.

    The maximum recommended dose is 1 gram/day.

    For rapid ascent, higher doses are beneficial for preventing acute mountain sickness beginning 24 to 48 hours before ascent and continuing for 48 hours while at high altitude.


    Open-angle Glaucoma:

    • tablet or intravenous injection: 250 mg 1 to 4 times a day.
    • SR capsule: 500 mg once or twice a day.

    Closed-angle glaucoma:

    • 250 to 500 mg intravenous, may repeat in 2 to 4 hours to a maximum of I gram/day.

    Seizure Prophylaxis

    • 8 to 30 mg/kg/day in 1 to 4 divided doses. Do not exceed 1 gram per day.
    • If this patient is already taking other anticonvulsants, the recommended starting dosage is 250 mg once a day. If acetazolamide is used alone, most patients with good renal function respond to daily doses ranging from 375 to 1000 mg. The optimum dosage for this patient with renal dysfunction is not known, and will depend on this patient’s clinical response and tolerance.

      What is the dose for a child?

      Glaucoma (over 1 year old)

      • Oral: 8 to 30 mg/kg/day or 300 to 900 mg/m²/day divided every 8 hours.
      • intravenous: 20 to 40 mg/kg/day divided every 6 hours. Maximum dose: 1 gram/day.

      Edema (over 1 year old)

      • Oral or intravenous: 5 mg/kg or 150 mg/m² once a day.

      Epilepsy (over 1 year old)

      • Oral: 8 to 30 mg/kg/day in 1 to 4 divided doses. Maximum dose is 1 gram/day.

      Hydrocephalus (under 1 year old)

      • Oral or intravenous: 20 to 100 mg/kg/day divided every 6 to 8 hours. Maximum dose is 2 grams/day.

      How is Acetazolamide available?

      Acetazolamide is available in the following dosage forms and strengths:

      • Capsule, extended-release: 500mg
      • Tablet, Oral: 125mg, 250mg

      What should I do in case of an emergency or overdose?

      In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

      What should I do if I miss a dose?

      If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


      Hello Health Group does not provide medical advice, diagnosis or treatment.

      Written by

      Stephanie Nera, RPh, PharmD


      Updated Jun 30, 2021

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