Acetazolamide

Acetazolamide comes as a tablet and capsule to take by mouth. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take acetazolamide exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you are taking the extended-release (long-acting) form of acetazolamide (Diamox Sequels), do not crush or chew the capsules.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

• blood in urine or stools;

• a seizure (convulsions);

• loss of movement in any part of your body;

• a blood cell disorder--sudden weakness or ill feeling, fever, chills, sore throat, mouth sores, pale skin, feeling tired or short of breath, rapid heart rate, nosebleeds, bleeding gums;

• liver problems--nausea, upper stomach pain or swelling, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

• signs of metabolic acidosis--confusion, vomiting, lack of energy, irregular heartbeats;

• signs of a kidney stone--pain in your side or lower back, blood in your urine, painful or difficult urination; or

• severe skin reaction--fever, sore throat, swelling in your face or tongue, burning in your eyes, skin pain followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Common side effects may include:

• nausea, vomiting, loss of appetite, diarrhea;

• numbness or tingling, especially in your arms and legs;

• drowsiness, confusion;

• hearing problems, ringing in your ears;

• increased urination; or

• altered sense of taste.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Administration

Administer orally or by direct IV injection.c d e

Do not administer IM; injection is painful.b e

Oral Administration

When an oral liquid preparation is needed, crush the appropriate number of tablets and suspend in a highly flavored carbohydrate syrup.a Can suspend up to 500 mg of acetazolamide in 5 mL of syrup; suspensions containing 250 mg per 5 mL are more palatable.a Alternatively, soften a tablet in 2 teaspoonsful of hot water and add 2 teaspoonsful of honey or syrup; swallow immediately.a

When the extended-release capsules are used for glaucoma, if adequate response is not achieved with twice-daily administration of this preparation, consider using other acetazolamide preparations that are administered more frequently (i.e., tablet, parenteral preparation) to achieve IOP control.d

IV Administration

For solution and drug compatibility information, see Compatibility under Stability.

Administer IV when rapid lowering of IOP is necessary or if patient is unable to take oral medication.a e

Reconstitute vial containing 500 mg of acetazolamide with 5 mL of sterile water for injection to provide a solution containing 100 mg/mL.a e

Dosage

Available as acetazolamide (oral preparations) and acetazolamide sodium; dosage expressed in terms of acetazolamide.c d e

Adjust dosage based on patient response and requirements.a

Pediatric Patients

8–30 mg/kg or 300–900 mg/m2 daily in 3 divided doses has been used.a

Children ≥12 years of age: 500 mg twice daily as extended-release capsules.d

Children ≥12 years of age: 500 mg twice daily as extended-release capsules.d

5–10 mg/kg every 6 hours has been used.a

Children ≥12 years of age: 500 mg once or twice daily as extended-release capsules.d Initiate 24–48 hours before ascent; continue for 48 hours while at high altitude or longer if needed to control symptoms.d

8–30 mg/kg daily in divided doses has been used.a c

5 mg/kg or 150 mg/m2 once daily in the morning has been used.a

Adults

Conventional tablets: 250 mg to 1 g daily.c For daily dosages >250 mg, administer in divided doses.c

Extended-release capsules: 500 mg twice daily.d

250 mg to 1 g daily.e For daily dosages >250 mg, administer in divided doses.e

Conventional tablets: 250 mg every 4 hours.c Some patients respond to short-term therapy with 250 mg twice daily.c

Extended-release capsules: 500 mg twice daily.d

250 mg every 4 hours.e Some patients respond to short-term therapy with 250 mg twice daily.e

Conventional tablets: 250 mg every 4 hours. a c Alternatively, 250 mg twice daily or an initial dose of 500 mg followed by 125–250 mg every 4 hours.a c

Extended-release capsules: 500 mg twice daily.d

250 mg every 4 hours.e Alternatively, 250 mg twice daily or an initial dose of 500 mg followed by 125–250 mg every 4 hours.e

Conventional tablets and extended-release capsules: 500 mg to 1 g daily in divided doses.c d Initiate 24–48 hours before ascent; continue for 48 hours while at high altitude or longer if needed to control symptoms.c d

125–250 mg twice daily starting 24 hours before ascent has been effective for prevention of acute mountain sickness; 500 mg (as extended-release capsules) every 24 hours also has been effective.f 750 mg daily may be more effective than 500 mg daily.f

125 mg at bedtime has been used for the management of high-altitude sleep disorders.f

For treatment of acute mountain sickness, some experts recommend 250 mg given within 24 hours of onset of symptoms and a second 250-mg dose 8 hours later.f

Conventional tablets: 8–30 mg/kg daily in divided doses.c

Usual dosage range: 375 mg to 1 g daily.c

When used in conjunction with other anticonvulsants, initiate at 250 mg once daily and increase dosage as needed.c

8–30 mg/kg daily in divided doses; usual dosage range is 375 mg to 1 g daily.e

When given in conjunction with other anticonvulsants, initiate at 250 mg once daily and increase dosage as needed.e

Conventional tablets: Initially, 250–375 mg (5 mg/kg) once daily in the morning.c

If patient fails to lose edema fluid after initial response, hold drug for 1 day. c To avoid loss of diuretic effect, administer intermittently (on alternate days or for 2 days followed by a drug-free day).c

Initially, 250–375 mg (5 mg/kg) once daily in the morning.e

If patient fails to lose edema fluid after initial response, hold drug for 1 day.e To avoid loss of diuretic effect, administer intermittently (on alternate days or for 2 days followed by a drug-free day).e

Conventional tablets: 250–375 mg once daily for 1 or 2 days, alternating with a drug-free day.c

250–375 mg once daily for 1 or 2 days, alternating with a drug-free day.e

250 mg 2 to 3 times daily has been used.a

Prescribing Limits

When used in glaucoma or seizure disorders, dosage >1 g daily is not associated with additional clinical benefit.c d e

When used for diuresis, increasing dosage does not produce greater response and may result in decreased response.c d e

Special Populations

Geriatric Patients

Select dosage with caution because of age-related decreases in hepatic, renal, and/or cardiac function and concomitant disease and drug therapy.d

Specific Drugs and Laboratory Tests

Adverse reactions, occurring most often early in therapy, include paresthesias, particularly a "tingling" feeling in the extremities, hearing dysfunction or tinnitus, loss of appetite, taste alteration and gastrointestinal disturbances such as nausea, vomiting and diarrhea; polyuria, and occasional instances of drowsiness and confusion.

Metabolic acidosis and electrolyte imbalance may occur.

Transient myopia has been reported. This condition invariably subsides upon diminution or discontinuance of the medication. Other occasional adverse reactions include urticaria, melena, hematuria, glycosuria, hepatic insufficiency, flaccid paralysis, photosensitivity and convulsions. Also see PRECAUTIONS: Information for Patients for possible reactions common to sulfonamide derivatives. Fatalities have occurred although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia and other blood dyscrasias (see WARNINGS).

Preparation and Storage of Parenteral Solution

Each 500 mg vial containing sterile Acetazolamide sodium should be reconstituted with at least 5 mL of Sterile Water for Injection prior to use. Reconstituted solutions retain their physical and chemical properties for 3 days under refrigeration at 2° to 8°C (36° to 46°F), or 12 hours at room temperature 20° to 25°C (68° to 77°F). CONTAINS NO PRESERVATIVE. The direct intravenous route of administration is preferred. Intramuscular administration is not recommended.

Glaucoma

Acetazolamide should be used as an adjunct to the usual therapy. The dosage employed in the treatment of chronic simple (open-angle) glaucoma ranges from 250 mg to 1 g of Acetazolamide per 24 hours, usually in divided doses for amounts over 250 mg. It has usually been found that a dosage in excess of 1 g per 24 hours does not produce an increased effect. In all cases, the dosage should be adjusted with careful individual attention both to symptomatology and ocular tension. Continuous supervision by a physician is advisable.

In treatment of secondary glaucoma and in the preoperative treatment of some cases of acute congestive (closed-angle) glaucoma, the preferred dosage is 250 mg every four hours, although some cases have responded to 250 mg twice daily on short-term therapy.

In some acute cases, it may be more satisfactory to administer an initial dose of 500 mg followed by 125 or 250 mg every four hours depending on the individual case. Intravenous therapy may be used for rapid relief of ocular tension in acute cases. A complementary effect has been noted when Acetazolamide has been used in conjunction with miotics or mydriatics as the case demanded.

Epilepsy

It is not clearly known whether the beneficial effects observed in epilepsy are due to direct inhibition of carbonic anhydrase in the central nervous system or whether they are due to the slight degree of acidosis produced by the divided dosage. The best results to date have been seen in petit mal in children. Good results, however, have been seen in patients, both in children and adult, in other types of seizures such as grand mal, mixed seizure patterns, myoclonic jerk patterns, etc. The suggested total daily dose is 8 to 30 mg per kg in divided doses. Although some patients respond to a low dose, the optimum range appears to be from 375 to 1000 mg daily. However, some investigators feel that daily doses in excess of 1 g do not produce any better results than a 1 g dose. When Acetazolamide is given in combination with other anticonvulsants, it is suggested that the starting dose should be 250 mg once daily in addition to the existing medications. This can be increased to levels as indicated above.

The change from other medications to Acetazolamide should be gradual and in accordance with usual practice in epilepsy therapy.

Congestive Heart Failure

For diuresis in congestive heart failure, the starting dose is usually 250 to 375 mg once daily in the morning (5 mg/kg). If, after an initial response, the patient fails to continue to lose edema fluid, do not increase the dose but allow for kidney recovery by skipping medication for a day.

Acetazolamide yields best diuretic results when given on alternate days, or for two days alternating with a day of rest.

Failures in therapy may be due to overdosage or too frequent dosage. The use of Acetazolamide does not eliminate the need for other therapy such as digitalis, bed rest, and salt restriction.

Drug-Induced Edema

Recommended dosage is 250 to 375 mg of Acetazolamide once a day for one or two days, alternating with a day of rest.

Note: The dosage recommendations for glaucoma and epilepsy differ considerably from those for congestive heart failure, since the first two conditions are not dependent upon carbonic anhydrase inhibition in the kidney which requires intermittent dosage if it is to recover from inhibitory effect of the therapeutic agent.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Refer to adult dosing. Oral: Initial doses should begin at the low end of the dosage range.

Capsules, tablets: Store at controlled room temperature.

Injection: Store intact vials at 20°C to 25°C (68°F to 77°F). Store reconstituted solutions for 3 days under refrigeration at 2°C to 8°C (36°F to 46°F), or 12 hours at room temperature, 20°C to 25°C (68°F to 77°F).

Ajmaline: Sulfonamides may enhance the adverse/toxic effect of Ajmaline. Specifically, the risk for cholestasis may be increased. Monitor therapy

Alpha-/Beta-Agonists (Indirect-Acting): Carbonic Anhydrase Inhibitors may increase the serum concentration of Alpha-/Beta-Agonists (Indirect-Acting). Monitor therapy

Amantadine: Carbonic Anhydrase Inhibitors may increase the serum concentration of Amantadine. Monitor therapy

Amphetamines: Carbonic Anhydrase Inhibitors may decrease the excretion of Amphetamines. Monitor therapy

Analgesics (Opioid): May enhance the adverse/toxic effect of Diuretics. Analgesics (Opioid) may diminish the therapeutic effect of Diuretics. Monitor therapy

CarBAMazepine: Carbonic Anhydrase Inhibitors may increase the serum concentration of CarBAMazepine. Monitor therapy

Carbonic Anhydrase Inhibitors: May enhance the adverse/toxic effect of other Carbonic Anhydrase Inhibitors. The development of acid-base disorders with concurrent use of ophthalmic and oral carbonic anhydrase inhibitors has been reported. Management: Avoid concurrent use of different carbonic anhydrase inhibitors if possible. Monitor patients closely for the occurrence of kidney stones and with regards to severity of metabolic acidosis. Avoid combination

CycloSPORINE (Systemic): AcetaZOLAMIDE may increase the serum concentration of CycloSPORINE (Systemic). Monitor therapy

Dexketoprofen: May enhance the adverse/toxic effect of Sulfonamides. Monitor therapy

Diacerein: May enhance the therapeutic effect of Diuretics. Specifically, the risk for dehydration or hypokalemia may be increased. Monitor therapy

Flecainide: Carbonic Anhydrase Inhibitors may increase the serum concentration of Flecainide. Monitor therapy

Fosphenytoin-Phenytoin: Carbonic Anhydrase Inhibitors may enhance the adverse/toxic effect of Fosphenytoin-Phenytoin. Specifically, the risk for osteomalacia or rickets may be increased. Monitor therapy

Lithium: Carbonic Anhydrase Inhibitors may decrease the serum concentration of Lithium. Monitor therapy

Mecamylamine: Sulfonamides may enhance the adverse/toxic effect of Mecamylamine. Avoid combination

Mefloquine: May diminish the therapeutic effect of Anticonvulsants. Mefloquine may decrease the serum concentration of Anticonvulsants. Management: Mefloquine is contraindicated for malaria prophylaxis in persons with a history of convulsions. Monitor anticonvulsant concentrations and treatment response closely with concurrent use. Consider therapy modification

Memantine: Carbonic Anhydrase Inhibitors may increase the serum concentration of Memantine. Monitor therapy

MetFORMIN: Carbonic Anhydrase Inhibitors may enhance the adverse/toxic effect of MetFORMIN. Specifically, the risk of developing lactic acidosis may be increased. Monitor therapy

Methenamine: Carbonic Anhydrase Inhibitors may diminish the therapeutic effect of Methenamine. Management: Consider avoiding this combination. Monitor for decreased therapeutic effects of methenamine if used concomitant with a carbonic anhydrase inhibitor. Consider therapy modification

Mianserin: May diminish the therapeutic effect of Anticonvulsants. Monitor therapy

Orlistat: May decrease the serum concentration of Anticonvulsants. Monitor therapy

Primidone: Carbonic Anhydrase Inhibitors may enhance the adverse/toxic effect of Primidone. Specifically, osteomalacia and rickets. Carbonic Anhydrase Inhibitors may decrease the serum concentration of Primidone. Monitor therapy

QuiNIDine: Carbonic Anhydrase Inhibitors may decrease the excretion of QuiNIDine. Monitor therapy

Salicylates: May enhance the adverse/toxic effect of Carbonic Anhydrase Inhibitors. Salicylate toxicity might be enhanced by this same combination. Management: Avoid these combinations when possible.Dichlorphenamide use with high-dose aspirin as contraindicated. If another combination is used, monitor patients closely for adverse effects. Tachypnea, anorexia, lethargy, and coma have been reported. Consider therapy modification

Sodium Bicarbonate: AcetaZOLAMIDE may enhance the adverse/toxic effect of Sodium Bicarbonate. Specifically, the risk of renal calculus formation may be increased. Monitor therapy

Sodium Phosphates: Diuretics may enhance the nephrotoxic effect of Sodium Phosphates. Specifically, the risk of acute phosphate nephropathy may be enhanced. Management: Consider avoiding this combination by temporarily suspending treatment with diuretics, or seeking alternatives to oral sodium phosphate bowel preparation. If the combination cannot be avoided, hydrate adequately and monitor fluid and renal status. Consider therapy modification

Trientine: Carbonic Anhydrase Inhibitor Diuretics may decrease the serum concentration of Trientine. Monitor therapy

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience nausea, vomiting, change in taste, diarrhea, lack of appetite, blurred vision, fatigue, loss of strength and energy, or headache. Have patient report immediately to prescriber signs of lactic acidosis (fast breathing, tachycardia, abnormal heartbeat, vomiting, fatigue, shortness of breath, severe loss of strength and energy, severe dizziness, feeling cold, or muscle pain or cramps), signs of fluid and electrolyte problems (mood changes, confusion, muscle pain or weakness, abnormal heartbeat, severe dizziness or passing out, tachycardia, increased thirst, seizures, loss of strength and energy, lack of appetite, urinary retention or change in the amount of urine passed, dry mouth, dry eyes, or nausea or vomiting), vision changes, hearing impairment, tinnitus, burning or numbness feeling, hematuria, urinary retention, change in amount of urine passed, signs of a severe sulfonamide reaction (rash; red, swollen, blistered, or peeling skin; red or irritated eyes; mouth, throat, nose, or eye sores; fever, chills, or pharyngitis; cough that is new or worse; loss of strength and energy; any bruising or bleeding; or signs of liver problems like dark urine, fatigue, lack of appetite, upset stomach or stomach pain, light-colored stools, throwing up, or jaundice), or injection site pain or irritation (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• aspirin (Ecotrin)
• phenytoin (Dilantin)
• primidone (Mysoline, Desoxyphenobarbital, Primaclone)
• other carbonic anhydrase inhibitors such as methazolamide (Neptazene), dorzolamide (Trusopt), and topiramate (Topamax)
• folic acid antagonists such as methotrexate (Trexall, Rheumatrex), trimethoprim (Bactrim, Septra, Primsol, Proloprim, Trimpex), pyrimethamine (Daraprim), pemetrexed (Alimtra), and raltitrexed (Tomudex)
• dexamphetamine/amphetamine salts (Adderall)
• quinidine (Duraquin, Quinalan, Quinact)
• methenamine (Hiprex, Urex, Mandelamine)
• lithium (Eskalith, Lithobid)
• cyclosporine (Gengraf, Neoral, Sandimmune)
• sodium bicarbonate

This is not a complete list of acetazolamide drug interactions. Ask your doctor or pharmacist for more information.

Take acetazolamide exactly as prescribed by your doctor. Follow the directions on your prescription label carefully.

The acetazolamide dose your doctor recommends will be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• weight

Glaucoma

The recommended dose range for acetazolamide is 250 mg-1000mg/day. The number of times acetazolamide will be given will depend on the formulation being given.

Acute Mountain Sickness

The recommended dose range for acetazolamide is 500 mg-1000mg/day. The number of times acetazolamide will be given will depend on the formulation being given.

Edema

Recommended dosage is 250 to 375 mg of acetazolamide once a day for one or two days, alternating with a day of rest.

Diuresis in Congestive Heart Failure

The starting dose is usually 250 to 375 mg once daily in the morning.

Epilepsy

The recommended dose range for acetazolamide is 375 to 1000 mg daily.

Mechanism of Action

Carbonic anhydrase inhibitor that decreases rate of aqueous humor formation, in that way decreasing intraocular pressure

Inhibits H+ ion excretion in renal tubule, increasing sodium, potassium, bicarbonate, and water excretion and producing alkaline diuresis

Inhibits carbonic anhydrase in CNS, which in turn decreases abnormal and excessive discharge from the CNS neurons

Absorption

Bioavailability: Rapidly absorbed orally

Tablet

• Onset: 1-1.5 hr
• Duration: 8-12 hr
• Peak plasma time: 1-4 hr

Sustained-release

• Onset: 2 hr
• Duration: 18-24 hr
• Peak plasma time: 8-18 hr

IV

• Onset: 5-10 min
• Duration: 4-5 hr
• Peak plasma time: 15 min

Distribution

Protein bound: 70-90%

Vd: 0.2 L/kg

Metabolism

Metabolism: None

Elimination

Half-life: 2-4 hr (tablet)

Dialyzable: Yes (hemodialysis)

Excretion: Urine 90%

500 to 1000 mg orally per day in divided doses
-May use immediate-release or extended-release as appropriate

Acute Mountain Sickness (AMS)/High Altitude Cerebral Edema (HACE) Prevention:
Guideline dose: 125 mg orally twice a day

AMS Treatment:
Guideline dose: 250 mg orally twice a day

Comments:
-Higher doses (1000 mg) are appropriate for rapid ascent, such as in rescue or military operations.
-Dosing should be to initiated 24 to 48 hours before ascent and continue for 48 hours while at high altitude, or longer as necessary to control symptoms.
-According to Wilderness Medical Society Consensus Guidelines, while higher doses are effective they are associated with more frequent and/or increased side effects.

Use: For the prevention or amelioration of symptoms associated with acute mountain sickness despite gradual ascent.

Safety and efficacy of extended-release (ER) capsules have not been established in patients younger than 12 years.
Safety and efficacy of immediate-release formulations have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.

Data not available

Animal studies have shown teratogenicity at doses in excess of 10 times the recommended dose in humans. There is no evidence of a direct association between this drug and birth defects during human pregnancy. In the Collaborative Perinatal Project (CCP), a retrospective study that evaluated 50,282 mother-child pairs, 12 had first trimester exposure to this drug with no anomalies observed. A total of 1024 anytime exposures were reported and the number of infants with malformations was less than expected (18 vs 18.06). There are no adequate and well-controlled studies in pregnancy women. Physicians are encouraged to register patients before fetal outcome is known (e.g., ultrasound, results of amniocentesis, etc) into the Antiepileptic Drug (AED) Pregnancy Registry at 1-888-233-2334 (-888-AED-AED4) or www.aedpregnancyregistry.org. This is an ongoing study at the Massachusetts General Hospital/Harvard Medical School. This study is designed to monitor the outcomes of pregnant women exposed to antiepileptic drugs in order to determine which therapies are associated with increased risk. AU TGA pregnancy category B3: Drugs which have been taken by only a limited number of pregnant women and women of childbearing age, without an increase in the frequency of malformation or other direct or indirect harmful effects on the human fetus having been observed. Studies in animals have shown evidence of an increased occurrence of fetal damage, the significance of which is considered uncertain in humans. US FDA pregnancy category C: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Benefit should outweigh risk AU TGA pregnancy category: B3 US FDA pregnancy category: C