Acetazolamide / Acetazolamide Sodium

Class and Category
Pharmacologic class: Carbonic anhydrase inhibitor
Therapeutic class: Anticonvulsant, antiglaucoma, diuretic

Indications and Dosages
👉   To treat chronic simple (open-angle) glaucoma

Adults. 500 mg twice daily.

Adults. 250 to 1,000 mg daily (divided for doses exceeding 250 mg).
As short-term therapy to treat secondary glaucoma; to treat acute angleclosure glaucoma preoperatively when delay of surgery is needed in order to lower intraocular pressure

Adults. 500 mg twice daily.

Adults. 250 mg twice daily or every 4 hr; or 500 mg initially, followed by 125 to 250 mg every 4 hr for severe acute glaucoma. Oral therapy usually started after initial I.V. dose.
To treat edema caused by congestive heart failure

Adults. Initial: 250 to 375 mg or 5 mg/kg daily in morning. Maintenance: 250 to 375 mg or 5 mg/kg on alternate days or for 2 days followed by a drug-free day.
To treat drug-induced edema

Adults. 250 to 375 mg once daily for 1 to 2 days alternating with a day of rest.
To treat seizures, including generalized tonic–colonic, absence, and mixed seizures, and myoclonic jerk patterns

Adults. 8 to 30 mg/kg daily in divided doses. Optimal: 375 to 1,000 mg daily.
When used with other anticonvulsants, initially, 250 mg daily, increased as needed to optimal dosage.
To prevent or relieve symptoms of acute mountain sickness.

Adults. 500 to 1,000 mg daily in divided doses, given 24 to 48 hr before ascent and continued for 48 hr or longer while at high altitude, as needed, to control symptoms.

Mechanism of Action
Inhibits the enzyme carbonic anhydrase, which normally appears in the eyes’ ciliary processes, brain’s choroid plexes, and kidneys’ proximal tubule cells. In the eyes, enzyme inhibition decreases aqueous humor secretion, which lowers intraocular pressure. In the brain, inhibition may delay abnormal, intermittent, and excessive discharge from neurons that cause seizures. In the kidneys, it increases bicarbonate excretion, which carries out water, potassium, and sodium, thus inducing diuresis and metabolic acidosis. This acidosis counteracts respiratory alkalosis and reduces symptoms of mountain sickness, including headache, dizziness, nausea, and dyspnea.

Chronic noncongestive closed-angle glaucoma; cirrhosis; hyperchloremic acidosis; hypersensitivity to acetazolamide, sulfonamides, other sulfonamide derivatives, or their components; hypokalemia; hyponatremia; severe hepatic, renal, or adrenocortical impairment; suprarenal gland failure

Amphetamines, Phenobarbital, Procainamide, Quinidine: Decreased excretion and possibly toxicity of these drugs
Corticosteroids: Increased risk of hypokalemia
Cyclosporine: Increased cyclosporine level, possibly nephrotoxicity or neurotoxicity
Diflunisal: Possibly significantly decreased intraocular pressure
Lithium: Increased excretion and decreased effectiveness of lithium
Primidone: Decreased serum and urine primidone levels
Salicylates: Increased risk of salicylate toxicity

Adverse Reactions
CNS: Ataxia, confusion, depression, disorientation, dizziness, drowsiness, fatigue, fever, flaccid paralysis, headache, lassitude, malaise, nervousness, paresthesia, seizures, tremor, weakness
EENT: Altered taste, tinnitus, transient myopia
GI: Anorexia, constipation, diarrhea, hepatic dysfunction, melena, nausea, vomiting GU: Crystalluria, decreased libido, glycosuria, hematuria, impotence, nephrotoxicity, phosphaturia, polyuria, renal calculi, renal colic, urinary frequency
HEME: Agranulocytosis, hemolytic anemia, leukopenia, pancytopenia, thrombocytopenia, thrombocytopenic purpura
SKIN: Photosensitivity, pruritus, rash, Stevens–Johnson syndrome, urticaria
Other: Acidosis, hyperuricemia, hypokalemia, weight loss

Childbearing Considerations
It is not known if drug causes fetal harm although animal studies suggest it might. Use with caution only if benefit to mother outweighs potential risk to fetus.

Drug may be present in breast milk.
A decision should be made to discontinue breastfeeding or the drug to avoid potential serious adverse reactions in the breastfed infant.

Nursing Considerations
  • Use acetazolamide cautiously in patients with calcium-based renal calculi, diabetes mellitus, gout, or respiratory impairment.
  • Know that acetazolamide may increase risk of hepatic encephalopathy in patients with hepatic cirrhosis.
  • Reconstitute each 500-mg vial with at least 5 ml sterile water for injection. Use within 12 hours because drug has no preservative unless refrigerated (use within 3 days).
  • Monitor blood tests during acetazolamide therapy to detect electrolyte imbalances.
  • Monitor fluid intake and output every 8 hours and body weight daily to detect excessive fluid and weight loss.
  • Advise patient to avoid hazardous activities if dizziness or drowsiness occurs.
  • Instruct patient who takes high doses of salicylates to notify prescriber immediately about evidence of salicylate toxicity, such as anorexia, tachypnea, and lethargy.
  • Tell patient if she plans to mountain climb, urge her to descend mountain gradually and to seek immediate medical care if symptoms of mountain sickness occur.

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