Acetazolamide

Acetazolamide

[tablets 10 cents each; vials for IV administration $48.37 each]

ADMINISTRATION ROUTES

  • PO, NG and IV

ALTERNATIVE NAMES

  • Diamox (Tab), Glaumox (Vial)

ICU INDICATIONS:

  1. Diuretic (particularly in the presence of metabolic alkalosis)
  2. Correction of severe metabolic alkalosis

PRESENTATION AND ADMINISTRATION

  • PO / NG: Diamox 250mg tablets (white); for NG use, crush prior to administration.
  • IV: Glaumox is supplied as a sterile powder requiring reconstitution. Each vial contains an amount of acetazolamide sodium equivalent to 500 mg of acetazolamide. Each 500-mg vial containing acetazolamide 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 24 hours under refrigeration at 2-8°C or 12 hours at room temperature

DOSAGE

  • For diuresis, the dose is usually 250-375 mg stat. If, after an initial response, the patient fails to continue to diurese, 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 2 days alternating with a day of rest.

PAEDIATRIC DOSE

  • The safety and effectiveness of acetazolamide in paediatric patients below the age of 12 years have not been established.

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY

  • No dose adjustment is required when administered for ICU indications (beware that acetazolamide is contraindicated in the presence of metabolic acidosis). This drug is not indicated in patients on renal replacement therapy.

CLINICAL PHARMACOLOGY

  • Acetazolamide is an enzyme inhibitor that acts on carbonic anhydrase, the enzyme that catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid.

CONTRAINDICATIONS

  1. Hypersensitivity to acetazolamide or other sulphonamides
  2. Metabolic acidosis
  3. Cirrhosis (risk of development of hepatic encephalopathy)

WARNINGS

  • Fatalities have occurred, although rarely, due to severe reactions to acetazolamide including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias.

PRECAUTIONS

  • General: Increasing the dose does not increase the diuresis and may increase the incidence of drowsiness and/or paresthesia. Increasing the dose often results in a decrease in diuresis.
  • Laboratory Tests: No tests are required in addition to routine ICU blood tests.
  • Drug/Laboratory Test Interactions: Acetazolamide interferes with the HPLC method of assay for theophylline. Interference with the theophylline assay by acetazolamide depends on the solvent used in the extraction; acetazolamide may not interfere with other assay methods for theophylline.

IMPORTANT DRUG INTERACTIONS FOR THE ICU

  • Acetazolamide modifies phenytoin metabolism with increased serum levels of phenytoin. Acetazolamide increases lithium excretion and the lithium levels may be decreased. Acetazolamide and sodium bicarbonate used concurrently increases the risk of renal calculus formation. Acetazolamide may elevate cyclosporine levels.

ADVERSE REACTIONS

  • Body as a Whole: Headache, malaise, fatigue, fever, pain at injection site, flushing, flaccid paralysis, anaphylaxis. Digestive: Gastrointestinal disturbances such as nausea, vomiting, diarrhoea.
  • Hepato-Biliary Disorders: Abnormal liver function, cholestatic jaundice, hepatic insufficiency, fulminant hepatic necrosis.
  • Metabolic/Nutritional: Metabolic acidosis, electrolyte imbalance, including hypokalaemia, hyponatraemia, loss of appetite, taste alteration, hyper/hypoglycemia.
  • Nervous: Drowsiness, paresthesia (including numbness and tingling of extremities and face), depression, excitement, ataxia, confusion, convulsions, dizziness.
  • Skin: Allergic skin reactions including urticaria, photosensitivity, Stevens-Johnson syndrome
  • Special Senses: Hearing disturbances, tinnitus, transient myopia.
  • Urogenital: Crystalluria, hematuria, glycosuria, renal failure polyuria.

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