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 medication is also used with other medications to treat high pressure inside the eye due to certain types of glaucoma. Acetazolamide belongs to a class of drugs known as carbonic anhydrase inhibitors. It works by decreasing the production of fluid inside the eye. It is also used to decrease a buildup of body fluids (edema) caused by heart failure or certain medications. Acetazolamide can work less well over time, so it is usually used only for a short period.

It has also been used with other medications to treat certain types of seizures (petit mal and unlocalized seizures).

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used for a certain condition causing a serious increase in pressure inside the skull (intracranial hypertension).

If you are taking the tablets, take this medication by mouth as directed by your doctor, usually 1 to 4 times daily. If you are taking the long-acting capsules, take this medication by mouth as directed by your doctor, usually 1 or 2 times daily. 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. The dosage is based on your medical condition and response to treatment.

Do not change brands or dosage forms of this medication without talking to your doctor or pharmacist. Not all forms of this medication work the same way.

To prevent altitude sickness, start taking acetazolamide 1 to 2 days before you start to climb. Keep taking it while you are climbing and for at least 48 hours after you have reached your final altitude. You may need to keep 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 (such as 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 your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.

When this medication is used for a long time, it may not work as well. Talk with your doctor if this medication stops working well.

Tell your doctor if your condition lasts or gets worse.

Dizziness, lightheadedness, or increased urination may occur, especially during the first few days as your body adjusts to the medication. Blurred vision, dry mouth, drowsiness, loss of appetite, nausea, vomiting, diarrhea, or changes in taste may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• tingling of the hands/feet
• hearing loss
• ringing in the ears
• unusual tiredness
• easy bleeding/bruising
• fast/irregular heartbeat
• muscle cramps/pain
• new or worsening eye pain
• decrease in vision
• mental/mood changes (such as confusion, difficulty concentrating)
• signs of liver disease (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• signs of kidney problems (such as painful urination, pink/bloody urine, change in the amount of urine)
• signs of infection (such as sore throat that doesn't go away, fever, chills)

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking acetazolamide, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• adrenal gland problems (such as Addison's disease)
• untreated mineral imbalance (such as low sodium/potassium, hyperchloremic acidosis)
• dehydration
• kidney disease
• liver disease
• breathing problems (such as chronic obstructive pulmonary disease-COPD, emphysema, lung infection)
• diabetes
• gout
• narrow-angle glaucoma
• overactive thyroid (hyperthyroidism)

While this medication can help you get used to high altitudes and help you tolerate quick climbs, it cannot completely prevent serious altitude sickness. Symptoms of serious altitude sickness may include shortness of breath, mental/mood changes (such as confusion, difficulty concentrating), lack of coordination/staggering walk, severe tiredness, or severe headache. If you develop any of these symptoms, it is very important that you descend to a lower altitude as quickly as possible to prevent serious, possibly fatal problems.

This drug may make you dizzy or drowsy or blur your vision. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness or clear vision until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

This drug may reduce the potassium levels in your blood. Your doctor may instruct you to add potassium-rich foods to your diet (such as bananas, orange juice) or prescribe potassium supplements to prevent potassium loss. Ask your doctor for more details.

This drug may rarely make your blood sugar rise, which can cause or worsen diabetes. Tell your doctor right away if you have symptoms of high blood sugar such as increased thirst/urination.

If you already have diabetes, check your blood sugar regularly as directed and share the results with your doctor. This medication may also lower your blood sugar. Symptoms of low blood sugar include sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness or tingling hands/feet. It is a good habit to carry glucose tablets or gel to treat low blood sugar. If you don't have these reliable forms of glucose, rapidly raise your blood sugar by eating a quick source of sugar such as table sugar, honey, or candy, or by drinking a glass of orange juice or non-diet soda. Tell your doctor right away about the reaction and the use of this product. To help prevent low blood sugar, eat meals on a regular schedule, and do not skip meals.

This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to its effects, especially dizziness and lightheadedness.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• lithium
• memantine
• methenamine
• orlistat
• certain drugs used to treat seizures (topiramate, zonisamide)

Check the labels on all your medicines because they may contain aspirin or aspirin-like drugs (salicylates), which can cause serious side effects if taken in large doses with this medication. However, if your doctor has told you to take low-dose aspirin to prevent heart attack or stroke (usually 81-162 milligrams a day), you should keep taking the aspirin unless your doctor tells you not to. Ask your doctor or pharmacist for more details.

Some products have ingredients that could worsen your swelling. Tell your pharmacist what products you are using, and ask how to use them safely (especially NSAIDs such as ibuprofen/naproxen).

This medication may interfere with certain lab tests, possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as complete blood count, potassium and sodium levels in the blood, liver function) may be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time for your next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.