acetazolamide: clinical use

Prescribing considerations

• Assess renal and hepatic function, electrolyte and acid–base status, sulfonamide hypersensitivity, respiratory disease, diabetes, urinary obstruction and renal-stone history.
• Review medicines for salicylates, antiseizure agents, lithium, ciclosporin, sodium bicarbonate and other carbonic anhydrase inhibitors.
• Diuretic effectiveness can diminish as metabolic acidosis develops.
• Counsel about serious skin reactions, blood dyscrasias, acute visual symptoms, pulmonary oedema and suicidal ideation.

Contraindications and cautions

• Hypersensitivity to acetazolamide, product excipients, sulfonamides or sulfonamide derivatives
• Depressed sodium or potassium concentrations
• Marked renal or hepatic disease or dysfunction, including hepatic cirrhosis
• Adrenal insufficiency
• Hyperchloraemic acidosis
• Long-term use in chronic non-congestive angle-closure glaucoma

Monitoring

• Baseline and periodic serum electrolytes and acid–base status
• Periodic full blood count during long-term treatment
• Renal and hepatic function according to clinical risk
• Blood glucose in diabetes or impaired glucose tolerance
• Clinical review for rash, infection, bleeding, visual change, renal calculi, mood change and respiratory symptoms

Clinical pharmacology

Carbonic anhydrase inhibition promotes alkaline diuresis through renal bicarbonate and cation loss, reduces aqueous-humour production and lowers intraocular pressure. Acetazolamide is eliminated unchanged in urine.

Formulation and product differences

• The oral product is a scored tablet that can be divided into equal parts.
• The injectable product is a powder requiring reconstitution; intravenous administration is preferred because intramuscular injection may be painful due to the alkaline solution.
• The reconstituted injection contains no antimicrobial preservative and requires controlled handling and disposal.

Tablet

Route: Oral

Strengths: 250 mg

Injection

Route: Parenteral

Strengths: 500 mg