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Pharmacologic class: Carbonic anhydrase inhibitor
Therapeutic class: Diuretic, antiglaucoma drug, anticonvulsant, altitude agent, urinary alkalinizer
Pregnancy risk category C
Inhibits carbonic anhydrase in kidney, decreasing water reabsorption and increasing excretion of sodium, potassium, and bicarbonate. Lowers intraocular pressure by decreasing aqueous humor production. May raise seizure threshold by reducing carbonic anhydrase in CNS, thereby decreasing neuronal conduction.
Capsules (sustained-release): 500 mg
Injection: 500 mg/vial
Tablets: 125 mg, 250 mg
Indications and dosages
➣ Open-angle (chronic simple) glaucoma (given with miotics)
Adults: 250 mg P.O. one to four times daily, or 500-mg sustained-release capsule P.O. once or twice daily. Don't exceed total daily dosage of 1 g.
➣ Preoperative treatment of closed-angle (secondary) glaucoma
Adults: 250 mg P.O. q 4 hours or 250 mg P.O. b.i.d.; in acute cases only, 500 mg P.O. followed by 125 to 250 mg P.O. q 4 hours. For rapid relief of increased intraocular pressure, 500 mg I.V., repeated in 2 to 4 hours; then 125 to 250 mg P.O. q 4 to 6 hours.
Children: 10 to 15 mg/kg/day P.O. in divided doses q 6 to 8 hours, or 5 to 10 mg/kg I.V. q 6 hours
➣ Seizure disorder (given with other anticonvulsants)
Adults and children: 250 mg P.O. daily when given with another anticonvulsant, or 8 to 30 mg/kg daily P.O. in one to four divided doses. Usual dosage range is 375 mg to 1 g daily.
➣ Drug-induced edema or edema secondary to heart failure
Adults: Initially, 250 to 375 mg P.O. daily. If diuresis fails, give dose on alternate days, or give for 2 days alternating with day of rest.
Children: 5 mg/kg P.O. daily, or 150 mg/m2 P.O. or I.V. once daily in morning
➣ Acute high-altitude (mountain) sickness
Adults: 500 mg to 1 g P.O. daily in divided doses, or sustained-release capsule q 12 to 24 hours. Dosing should begin 24 to 48 hours before ascent and continue during ascent and for 48 hours after reaching desired altitude. For rapid ascent, 1-g P.O. dose is recommended.
• Mild renal failure
• Acute pancreatitis
• Alkalosis after open-heart surgery
• Hereditary ataxia
• Peptic ulcer
• Periodic paralysis
• Renal calculi
• Phenobarbital or lithium overdose
• Hydrocephalus in infants
• Hypersensitivity to drug or sulfonamides
• Adrenocortical insufficiency
• Closed-angle glaucoma
• Severe pulmonary obstruction
• Severe renal disease, hypokalemia, hyponatremia
• Hepatic disease
Use cautiously in:
• respiratory, renal, or hepatic disease; diabetes mellitus, hypercalcemia, gout, adrenocortical insufficiency
• pregnant or breastfeeding patients.
☞ Before giving, ask if patient is pregnant. Drug may cause fetal toxicity.
• Direct I.V. administration is preferred. When giving by direct I.V. route, reconstitute 500-mg vial with more than 5 ml of sterile water for injection; administer over 1 minute.
• When giving drug intermittently by I.V. infusion, further dilute with normal saline solution or dextrose solution and infuse over 4 to 8 hours.
• Be aware that I.M. administration is painful because solution is alkaline.
• If necessary, crush tablets and mix in nonsweet, nonalcoholic syrup or non-glycerin solution.
CNS: weakness, nervousness, irritability, drowsiness, confusion, dizziness, depression, tremor, headache, paresthesia, flaccid paralysis, seizures
EENT: transient myopia, tinnitus, hearing dysfunction, sensation of lump in throat
GI: nausea, vomiting, diarrhea, constipation, melena, abdominal distention, dry mouth, anorexia
GU: dysuria, hematuria, glycosuria, polyuria, crystalluria, renal colic, renal calculi, uremia, sulfonamide-like renal lesions, renal failure
Hematologic: thrombocytopenia, leukopenia, agranulocytosis, hemolytic anemia, thrombocytopenic purpura, pancytopenia, bone marrow depression with aplastic anemia
Hepatic: hepatic insufficiency
Metabolic: hypokalemia, hyperglycemia and glycosuria, hyperuricemia and gout, metabolic acidosis, hyperchloremic acidosis
Skin: rash, pruritus, urticaria, photosensitivity, hirsutism, cyanosis
Other: altered taste and smell, weight loss, fever, excessive thirst, pain at I.M. injection site, hypersensitivity reaction, Stevens-Johnson syndrome
Drug-drug. Amphetamines, procainamide, quinidine, tricyclic antidepressants: decreased excretion and enhanced or prolonged effect of these drugs, leading to toxicity
Amphotericin B, corticosteroids, corticotrophin, other diuretics: increased risk of hypokalemia
Lithium, phenobarbital, salicylates: increased excretion of these drugs, possibly reducing their efficacy
Methenamine compounds: inactivation of these drugs
Phenytoin, primidone: severe osteomalacia
Salicylates: increased risk of salicylate toxicity
Drug-diagnostic tests. Ammonia, bilirubin, calcium, chloride, glucose, uric acid: increased levels
Thyroid iodine uptake: decreased in patients with hyperthyroidism or normal thyroid function
Urinary protein (with some reagents): false-positive result
Drug-behaviors. Sun exposure: increased risk of photosensitivity
☞ Evaluate for signs and symptoms of sulfonamide sensitivity; drug can cause fatal hypersensitivity.
☞ Monitor laboratory test results for hematologic changes; blood glucose, potassium, bicarbonate, and chloride levels; and liver and kidney function changes.
• Observe for signs and symptoms of bleeding tendency.
• Monitor fluid intake and output.
• Advise patient to take drug with food if GI upset occurs.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Tell patient to eat potassium-rich foods (such as seafood, bananas, and oranges) if taking drug long term or receiving other potassium-depleting drugs.
• Advise patient to avoid activities that can cause injury. Advise him to use soft toothbrush and electric razor to avoid gum and skin injury.
• Tell patient to report significant numbness or tingling.
• Inform patient that he'll undergo regular blood testing during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and behaviors mentioned above.
AcetazolamideA heterocyclic sulphonamide used to manage respiratory acidosis by inhibiting renal carbonic anhydrase, which increases renal excretion of Na+, K+, and bicarbonate, and reduces ammonia excretion. Acetazolamide is also used to reduce fluid retention in congestive heart failure, control secondary glaucoma and preoperatively in acute angle-closure glaucoma, and may be of use in seizures, especially absence seizures.
Effect Reduced serum pH; increased urine pH