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

Methazolamide belongs to the class of medications called carbonic anhydrase inhibitors. It is used to treat open-angle glaucoma, where higher than normal pressure within the eye. It is also used before surgery associated with acute angle-closure glaucoma, where surgery is delayed in order to lower the pressure inside the eye.

Fluid is constantly being formed and drained out of the eye. When this fluid does not drain out of the eye properly, pressure inside the eye increases. Methazolamide works by decreasing the production of fluid in the eye. It begins to reduce the pressure in the eye within 2 to 4 hours, with its maximum effect occurring at about 6 to 8 hours.

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 white, round, biconvex, straight-edged tablet, engraved "APO" on one side, scored and engraved "MZ" over "50" on the other, contains methazolamide 50 mg. Nonmedicinal ingredients: methylcellulose, colloidal silicon dioxide, and magnesium stearate.

How should I use this medication?

The usual recommended dose of methazolamide is 50 mg to 100 mg by mouth taken 2 to 3 times daily, as recommended by your doctor. This medication may be used at the same time as other medications for the eye.

If this medication causes upset stomach, it may be taken with food.

Many things can affect the dose of a 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 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?

Methazolamide should not be taken by anyone who:

  • is allergic to methazolamide or to any of the ingredients in the medication
  • is allergic to "sulfa" medications (e.g., sulfamethoxazole)
  • is allergic to "thiazide" diuretics (e.g., hydrochlorothiazide)
  • has a form of glaucoma other than chronic open angle glaucoma or secondary glaucoma
  • has Addison's disease or other diseases where the adrenal glands do not work properly
  • has low levels of potassium or sodium in the blood
  • has severe kidney disease
  • has severe liver disease

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.

  • diarrhea
  • dizziness or lightheadedness
  • drowsiness
  • general feeling of discomfort or illness
  • headache
  • increase in frequency of urination or amount of urine
  • increased sensitivity to sunlight
  • loss of appetite
  • metallic taste in mouth
  • nausea or vomiting
  • numbness, tingling, or burning in hands, fingers, feet, toes, mouth, lips, tongue, or anus
  • weakness
  • weight loss

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

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

  • blood in urine
  • bloody or black, tarry stools
  • confusion
  • darkening of the urine
  • depression
  • difficult urination
  • fever
  • hives, itchy skin, skin rash, or sores
  • muscle weakness (severe)
  • pain in the lower back
  • pain or burning while urinating
  • ringing or buzzing in the ears
  • sensitivity to light
  • sore throat
  • sudden decrease in the amount of urine
  • unusual bruising or bleeding
  • unusual tiredness or weakness
  • yellow eyes or skin

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • convulsions (seizures)
  • difficulty breathing
  • shortness of breath

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 using 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 use this medication.

Chronic lung disease: People with chronic lung diseases, such as emphysema, should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Diabetes: People with diabetes should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. You will probably need to test your blood sugar levels more often when you are taking methazolamide.

Electrolyte balance: Methazolamide causes your body to lose potassium, especially when first starting the medication. Your doctor will monitor your electrolyte levels while you are taking this medication. People who have low potassium levels should not take this medication.

Gout: People with gout should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney disease: People with kidney disease should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. You will probably need to have regular kidney tests while you are taking this medication. People with severely impaired kidney function should not take methazolamide.

Liver disease: People with liver disease should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. People with severely impaired liver function should not use methazolamide.

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: It is not known if methazolamide passes into breast milk. If you are a breast-feeding mother and are taking this medication, 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 methazolamide and any of the following:

  • acetylsalicylic acid (ASA)
  • cyclosporine
  • primidone
  • quinidine
  • systemic corticosteroids (e.g., prednisone)

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.