Carbonic anhydrase inhibitors are used to treat glaucoma. Acetazolamide is also used as an anticonvulsant to control certain
seizures in the treatment of epilepsy. It is also sometimes used to prevent or lessen some effects in mountain climbers who climb to
high altitudes, and to treat other conditions as determined by your doctor.
These medicines are available only with your doctor's prescription, in the following dosage forms:
Oral
Acetazolamide
Extended-release capsules (U.S. and Canada)
Tablets (U.S. and Canada)
Dichlorphenamide
Tablets (U.S.)
Methazolamide
Tablets (U.S. and Canada)
Parenteral
Acetazolamide
Injection (U.S. and Canada)
Before Using This Medicine
In deciding to use a medicine, the risks of taking the medicine must
be weighed against the good it will do. This is a decision you and
your doctor will make. For carbonic anhydrase inhibitors, the
following should be considered:
Allergies
Tell your doctor if you have ever had any unusual or allergic reaction to carbonic anhydrase inhibitors, sulfonamides (sulfa
drugs), or thiazide diuretics (a type of water pill). Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.
Pregnancy
Carbonic anhydrase inhibitors have not been studied in pregnant women. However, studies in animals have shown that carbonic
anhydrase inhibitors cause birth defects. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.
Breast-feeding
Carbonic anhydrase inhibitors may pass into the breast milk. These medicines are not recommended during
breast-feeding, because they may cause unwanted effects in nursing babies. It may be necessary for you to use another medicine or to
stop breast-feeding during treatment. Be sure you have discussed this with your doctor.
Children
Although there is no specific information comparing use of carbonic anhydrase inhibitors in children with use in other age
groups, these medicines are not expected to cause different side effects or problems in children than they do in adults.
Older adults
Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work
exactly the same way they do in younger adults. Although there is no specific information comparing use of carbonic anhydrase inhibitors
in the elderly with use in other age groups, these medicines are not expected to cause different side effects or problems in older people than they do in younger adults.
Other medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used
together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be
necessary. When you are using carbonic anhydrase inhibitors, it is especially important that your health care professional know if you are using any of the following:
- Amphetamines or
- Mecamylamine (e.g., Inversine) or
- Quinidine (e.g., Quinidex)—Use of carbonic anhydrase inhibitors may increase the chance of side effects
- Methenamine (e.g., Mandelamine)—Use of carbonic anhydrase inhibitors may decrease the effectiveness of methenamine
Other medical problems
The presence of other medical problems may affect the use of carbonic anhydrase inhibitors. Make sure you tell your doctor if you have any other medical problems, especially:
Type 2 diabetes mellitus
Use of carbonic anhydrase inhibitors may increase the patient's blood and urine sugar concentrations.
Emphysema or other chronic lung disease
Use of carbonic anhydrase inhibitors may increase the risk of acidosis (shortness of breath,
troubled breathing).
Gout or
Low blood levels of potassium or sodium
Use of carbonic anhydrase inhibitors may make the condition worse.
Kidney disease or stones
Higher blood levels of carbonic anhydrase inhibitors may result, which may increase the chance of side
effects; also, these medicines may make the condition worse.
Liver disease
Use of carbonic anhydrase inhibitors may increase the
risk of electrolyte imbalance and may make the condition worse.
Underactive adrenal gland (Addison's disease)
Use of carbonic anhydrase inhibitors may increase the risk of electrolyte imbalance.
Proper Use of This Medicine
Take this medicine only as directed . Do not take more of it and do not take it more often than your doctor ordered. To do so may
increase the chance of side effects without increasing the effectiveness of this medicine.
This medicine may be taken with meals to lessen the chance of stomach upset. However, if stomach upset (nausea or vomiting)
continues, check with your doctor.
This medicine may cause an increase in the amount of urine or in your frequency of urination. If you continue to take the medicine
every day, these effects should lessen or stop. To keep the increase in urine from affecting your nighttime sleep:
If you are to take a single dose a day, take it in the morning after breakfast.
If you are to take more than one dose a day, take the last dose no later than 6 p.m., unless otherwise directed by your doctor.
However, it is best to plan your dose or doses according to a schedule that will least affect your personal activities and sleep.
Ask your health care professional to help you plan the best time to take this medicine.
Dosing
The doses of carbonic anhydrase inhibitors will be different for different patients. Follow your doctor's orders or the
directions on the label . The following information includes only the average doses of these medicines. If your dose is different, do
not change it unless your doctor tells you to do so.
The number of capsules or tablets that you take depends on the strength of the medicine. Also, the number of doses you take each
day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are taking
the carbonic anhydrase inhibitor .
For acetazolamide
For oral dosage form (extended-release capsules):
For glaucoma:
Adults—500 milligrams (mg) two times a day, in the morning and evening.
Children—Use and dose must be determined by your doctor.
For oral dosage form (tablets):
For glaucoma:
Adults—250 mg one to four times a day.
Children—Dose is based on body weight and must be determined by your doctor. The usual dose is 10 to 15 mg per kilogram (kg) (4.5 to 6.8
mg per pound) of body weight a day in divided doses.
For injection dosage form:
For glaucoma:
Adults—500 mg, injected into a muscle or vein, for one dose.
Children—Dose is based on body weight and must be determined by your
doctor. The usual dose is 5 to 10 mg per kg (2.3 to 4.5 mg per
pound) of body weight every six hours, injected into a muscle or
vein.
For dichlorphenamide
For oral dosage form (tablets):
For glaucoma:
Adults—25 to 50 milligrams (mg) one to three times a day.
Children—Use and dose must be determined by your doctor.
For methazolamide
For oral dosage form (tablets):
For glaucoma:
Adults—50 to 100 milligrams (mg) two or three times a day.
Children—Use and dose must be determined by your doctor.
Missed dose
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the
missed dose and go back to your regular dosing schedule. Do not double doses.
Storage
To store this medicine:
Keep out of the reach of children.
Store away from heat and direct light.
Do not store the capsule or tablet form of this medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or
moisture may cause the medicine to break down.
Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.
Precautions While Using This Medicine
This medicine may cause some people to feel drowsy, dizzy, lightheaded, or more tired than they are normally. Make sure you
know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert .
It is important that your doctor check your progress at regular visits. Your doctor may want to do certain tests to see if the
medicine is working properly or to see if certain side effects may be occurring without your knowing it.
This medicine may cause a loss of potassium from your body . To help prevent this, your doctor may want you to eat or drink foods that
have a high potassium content (for example, orange or other citrus fruit juices) or take a potassium supplement. It is very important
to follow these directions. Also, it is important not to change your diet on your own. This is more important if you are already on a
special diet (as for diabetes) or if you are taking a potassium supplement. Extra potassium may not be necessary and, in some cases,
too much potassium could be harmful.
For diabetic patients:
This medicine may raise blood and urine sugar levels. While you are using this medicine, be especially careful in testing for sugar in
your blood or urine. If you have any questions about this, check with your doctor.
Your doctor may want you to increase the amount of fluids you drink while you are taking this medicine. This is to prevent kidney
stones. However, do not increase the amount of fluids you drink without first checking with your doctor.
For patients taking acetazolamide as an anticonvulsant:
If you have been taking acetazolamide regularly for several weeks or more, do not suddenly stop taking it . Your doctor may want you to
reduce gradually the amount you are taking before stopping completely.
Side Effects of This Medicine
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they
do occur they may need medical attention.
Check with your doctor immediately if either of the following side effects occurs:
- shortness of breath or trouble in breathing
- unusual tiredness or weakness
- blood in urine
- difficult urination
- mental depression
- pain in lower back
- pain or burning while urinating
- sudden decrease in amount of urine
- bloody or black, tarry stools
- clumsiness or unsteadiness
- confusion
- convulsions (seizures)
- darkening of urine
- fever
- hives, itching of skin, skin rash, or sores
- muscle weakness (severe)
- pale stools
- ringing or buzzing in the ears
- sore throat
- trembling
- unusual bruising or bleeding
- yellow eyes or skin
Symptoms of too much potassium loss:
- dryness of mouth
- increased thirst
- irregular heartbeats
- mood or mental changes
- muscle cramps or pain
- nausea or vomiting
- unusual tiredness or weakness
- weak pulse
Also, check with your doctor if you have any changes in your vision (especially problems with seeing faraway objects) when you first
begin taking this medicine.
Other side effects may occur that usually do not need medical
attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any
of the following side effects continue or are bothersome:
More common
- diarrhea;
- general feeling of discomfort or illness
- increase in frequency of urination or amount of urine (rare with methazolamide)
- loss of appetite
- metallic taste in mouth
- nausea or vomiting
- numbness, tingling, or burning in hands, fingers, feet, toes, mouth, lips, tongue, or anus
- weight loss
Less common or rare:
- constipation
- dizziness or light headedness
- drowsiness
- feeling of choking or lump in the throat
- headache
- increased sensitivity of eyes to sunlight
- loss of taste and smell
- nervousness or irritability
Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.
The information contained above is intended as an educational aid
only. It is not intended as medical advice for individual conditions or treatment. It is not a substitute for a medical exam, nor does it replace the need for services provided by medical professionals. Talk to your doctor, nurse or pharmacist before taking any
prescription or over the counter drugs (including any herbal medicines or supplements) or following any treatment or regimen.
Only your doctor, nurse, or pharmacist can provide you with advice on what is safe and effective for you.