Intravenous Adjunct in open-angle glaucoma, Preoperative management of angle-closure glaucoma
Adult: 250-1,000 mg daily, may be given in divided doses for amounts over 250 mg daily.
Intravenous Diuresis, Oedema
Adult: Fluid retention in CHF and drug-induced oedema: 250-375 mg once daily or on alternate days. Fluid retention associated with pre-menstrual tension: 125-375 mg as a single daily dose.
Intravenous Epilepsy
Adult: As monotherapy or adjunct with other antiepileptics: 250-1,000 mg daily in divided doses. Child: 8-30 mg/kg daily in divided doses. Max: 750 mg/day.
Oral Epilepsy
Adult: As monotherapy or adjunct with other antiepileptics: 250-1,000 mg daily in divided doses. Child: 8-30 mg/kg daily in divided doses. Max: 750 mg/day.
Oral Diuresis, Oedema
Adult: Fluid retention in CHF and drug-induced oedema: 250-375 mg once daily or on alternate days. Intermittent treatment is needed for continued efficacy. Fluid retention associated with pre-menstrual tension: 125-375 mg as a single daily dose.
Oral Adjunct in open-angle glaucoma, Preoperative management of angle-closure glaucoma
Adult: As conventional tab: 250-1,000 mg daily, may be given in divided doses for amounts over 250 mg daily. As extended-release cap: 500 mg bid.
Oral Prophylaxis of high-altitude disorders
Adult: 500-1,000 mg daily in divided doses, preferably 24-48 hours before ascent, then continue for at least 48 hours while at high altitude, or as necessary to control symptoms.
Renal Impairment
Severe: Contraindicated.
Hepatic Impairment
Severe: Contraindicated.
Administration
Should be taken with food.
Reconstitution
IV: Add at least 5 mL of sterile water for inj to provide a solution containing not more than 100 mg/mL.
Contraindications
Hypersensitivity to sulfonamides. Na and/or K depletion, suprarenal gland failure, hyperchloraemic acidosis, hepatic cirrhosis, adrenocortical insufficiency, long term use in chronic non-congestive angle-closure glaucoma. Severe renal and hepatic impairment.
Special Precautions
Patients with diabetes mellitus, respiratory acidosis, impaired alveolar ventilation (e.g. pulmonary obstruction, emphysema), potential urinary tract obstruction, history of renal calculi. Concomitant use with high-dose aspirin. Mild to moderate renal and hepatic impairment. Elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Metabolic acidosis, electrolyte imbalance (e.g. hypokalaemia, hyponatraemia), impaired mental alertness and physical coordination, suicidal ideation and behaviour, growth retardation (children in long-term therapy), acute generalised exanthematous pustulosis. Ear and labyrinth disorders: Tinnitus, impaired hearing. Eye disorders: Transient myopia. Gastrointestinal disorders: Nausea, vomiting, diarrhoea. General disorders and admin site conditions: Fever, malaise, fatigue, ataxia, inj site pain. Hepatobiliary disorders: Abnormal liver function, hepatitis, cholestatic jaundice. Metabolism and nutrition disorders: Thirst, hyperglycaemia, hypoglycaemia. Nervous system disorders: Headache, paraesthesia, dysgeusia, flaccid paralysis. Psychiatric disorders: Irritability, depression, excitement, anorexia, confusion. Renal and urinary disorders: Polyuria, haematuria, glycosuria, crystalluria, renal calculi, colic or lesion; renal failure. Reproductive system and breast disorders: Decreased libido. Skin and subcutaneous tissue disorders: Rash, urticaria, photosensitivity. Vascular disorders: Flushing. Potentially Fatal: Rarely, severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, agranulocytosis, aplastic anaemia, blood dyscrasias, fulminant hepatic necrosis and anaphylaxis.
This drug may cause dizziness, drowsiness and myopia, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor CBC with differential, serum electrolytes and IOP at baseline and periodically thereafter; growth (children). Assess for allergy history prior to treatment initiation. Monitor for signs of suicidal ideation and behaviour; signs of excessive dosing and acidosis especially in elderly.
Overdosage
Symptoms: Electrolyte imbalance, acidotic state and CNS effects. Management: Symptomatic and supportive treatment. May administer bicarbonate to correct acidotic state.
Drug Interactions
May increase serum levels of anticonvulsants (e.g. phenytoin, carbamazepine). May potentiate the effects of folic acid antagonists, hypoglycaemics, and oral anticoagulants. May require dose adjustments when co-administered with cardiac glycosides or hypertensive agents. May increase excretion of lithium. May reduce serum level of primidone. May enhance effects of amphetamines and quinidine. May prevent the urinary antiseptic effect of methenamine. May elevate serum ciclosporin levels. Increased risk of renal calculus formation with Na bicarbonate. Potentially Fatal: Increased risk of severe acidosis and CNS toxicity with high-dose aspirin.
Lab Interference
May result to false-negative aldosterone/renin ratio (ARR). May interfere with HPLC theophylline assay and serum uric acid levels. May lead to false-positive results for urinary protein tests.
Action
Description: Mechanism of Action: Acetazolamide reversibly inhibits the carbonic anhydrase enzyme leading to reduced hydrogen ion secretion at renal tubules and increased renal excretion of Na, K, bicarbonate and water. It also decreases the production of aqueous humour in the eyes to reduce intraocular pressure (IOP) and inhibits carbonic anhydrase in the CNS to retard abnormal and excessive discharge from CNS neurons. Onset: Immediate-release tab: 1-1.5 hours; Extended-release cap: 2 hours; IV: 2-10 minutes. Duration: Inhibition of aqueous humour secretion: 8-12 hours (conventional tab); 18-24 hours (extended-release cap); 4-5 hours (IV). Pharmacokinetics: Absorption: Fairly rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration: 1-4 hours (conventional tab); 3-6 hours (extended-release cap); 15 minutes (IV). Distribution: Distributed into body tissues with high concentration in RBCs and renal cortex. Crosses the blood-brain barrier. Crosses placenta and enters breast milk. Plasma protein binding: 95%. Excretion: Via urine: 70-100% (conventional tab, IV); 47% (extended-release cap, as unchanged drug within 24 hours). Half-life: 2.4-5.8 hours.
Chemical Structure
Acetazolamide Source: National Center for Biotechnology Information. PubChem Database. Acetazolamide, CID=1986, https://pubchem.ncbi.nlm.nih.gov/compound/Acetazolamide (accessed on Jan. 20, 2020)
Storage
Store between 20-25°C. Protect from light and moisture. Reconstituted IV solution: Store between 2-8°C.
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