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

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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