Carbonic anhydrase inhibitor

Class Name: carbonic anhydrase inhibitor (Oral route, Parenteral route)

Commonly used brand name(s)

In the U.S.

• Diamox Sequels
• Glauctabs
• Keveyis
• Neptazane

Available Dosage Forms:

• Tablet
• Capsule, Extended Release

Uses for this Medicine

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.

Before using this Medicine

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

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.

Geriatric

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.

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.

Interactions with 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 taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using medicines in this class with any of the following medicines is not recommended. Your doctor may decide not to treat you with a medication in this class or change some of the other medicines you take.

• Aspirin
• Methenamine

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acyclovir
• Adefovir
• Amphetamine
• Arsenic Trioxide
• Aspirin
• Benzphetamine
• Carbamazepine
• Ceritinib
• Dextroamphetamine
• Digitalis
• Droperidol
• Furosemide
• Levomethadyl
• Lisdexamfetamine
• Lithium
• Memantine
• Methamphetamine
• Methotrexate
• Porfimer
• Primidone
• Proscillaridin
• Quinidine
• Sotalol
• Topiramate
• Valacyclovir

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of medicines in this class. 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 dose medicines in this class 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 amount of medicine 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 using the medicine.

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 altitude sickness:
    • Adults—500 mg one or two times a day.
    • 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 epilepsy:
    • Adults and children—Dose is based on body weight and must be determined by your doctor. The usual dose is 10 mg per kg (4.5 mg per pound) of body weight a day in divided doses.
  • For altitude sickness:
    • Adults—250 mg two to four times a day.
    • Children—Use and dose must be determined by your doctor.
• 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

Keep out of the reach of children.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Do not keep outdated medicine or medicine no longer needed.

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 any of the following side effects occur:

Rare

• Shortness of breath or trouble in breathing

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

More common

• Unusual tiredness or weakness

Less common

• Blood in urine
• difficult urination
• mental depression
• pain in lower back
• pain or burning while urinating
• sudden decrease in amount of urine

Rare

• Bloody or black, tarry stools
• clumsiness or unsteadiness
• convulsions (seizures)
• darkening of urine
• fever
• hives, itching of skin, skin rash, or sores
• 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.

Some 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. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

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 lightheadedness
• 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 may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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