Acetazolamide

CLINICAL USE

Carbonic anhydrase inhibitor:

  • Glaucoma
  • Diuretic
  • Epilepsy

    DOSE IN NORMAL RENAL FUNCTION

    Glaucoma/Epilepsy: 0.25–1 g daily in divided dosesDiuretic: 250–375 mg daily

    PHARMACOKINETICS

  • Molecular weight                           :222.2
  • %Protein binding                           :70–90
  • %Excreted unchanged in urine     : 100
  • Volume of distribution (L/kg)       :0.2
  • half-life – normal/ESRD (hrs)      :3–6/26

    DOSE IN RENAL IMPAIRMENT

    GFR (mL/MIN)

  • 20 to 50     : 250 mg up to 4 times a day
  • 10 to 20     : 250 mg up to twice a day
  • <10           : 250 mg daily

    DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

  • CAPD                :Not dialysed. Dose as in GFR <10 mL/min
  • HD                     :Unlikely dialysability. Dose as in GFR <10 mL/min.
  • HDF/high flux   :Unknown dialysability. Dose as in GFR <10 mL/min
  • CAV/VVHD      :Unknown dialysability. Dose as in GFR 10 to 20 mL/min

    IMPORTANT DRUG INTERACTIONS

    Potentially hazardous interactions with other drugs

  • Analgesics: high dose aspirin reduces excretion (risk of toxicity)
  • Anti-arrhythmics: increased toxicity if hypokalaemia occursAntibacterials: effects of methenamine antagonised
  • Anti-epileptics: increased risk of osteomalacia with phenytoin, primidone and phenobarbital; concentration of carbamazepine increased and primidone reduced
  • Antihypertensives: enhanced hypotensive effect
  • Antipsychotics: increased risk of ventricular arrhythmias due to hypokalaemia
  • Atomoxetine: increased risk of ventricular arrhythmias due to hypokalaemia
  • Beta-blockers: increased risk of ventricular arrhythmias due to hypokalaemia with sotalol
  • Cardiac glycosides: increased toxicity if hypokalaemia occurs
  • Lithium: lithium excretion increased

    ADMINISTRATION

    Reconstition

    Add at least 5 mL of water for injection

    Route

    Oral, IM, IV

    Rate of Administration

    Give slow IV

    Comments

    Avoid IM due to alkaline pH Monitor for signs of extravasation and skin necrosis during administration

    OTHER INFORMATION

  • Use cautioned in severe renal failure
  • Acetazolamide sodium (Diamox) parenteral contains 2.36 millimoles of sodium per vial
  • Severe metabolic acidosis may occur in the elderly and in patients with reduced renal function
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