SPIRONOLACTONE

What it is

Spironolactone Viatris is available as an uncoated tablet in two strengths: 25 mg and 100 mg tablets. Spironolactone is a specific pharmacological antagonist of aldosterone, acting primarily through competitive binding of receptors at the aldosterone dependent sodium–potassium exchange site in the distal convoluted renal tubule. It causes increased amounts of sodium and water to be excreted whilst potassium is retained, and has both diuretic and antihypertensive activity.

Approved indications

— Essential hypertension. — Adjunctive therapy in malignant hypertension. — Diuretic-induced hypokalaemia when other measures are considered inappropriate or inadequate. — Prophylaxis of hypokalaemia in patients taking digitalis when other measures are considered inadequate or inappropriate. — Congestive cardiac failure. — Hepatic cirrhosis with ascites and oedema. — Nephrotic syndrome. — Diagnosis and treatment of primary hyperaldosteronism. — Hirsutism in females.

Dosing overview

For essential hypertension, the dose is 50 to 100 mg per day, which may be given either in divided doses or as a single daily dose. Dosage should be adjusted according to response, but maximum effect may not occur for up to two weeks after starting treatment.

Key safety warnings

Concomitant use of spironolactone with angiotensin converting enzyme inhibitors, non-steroidal anti-inflammatory drugs, angiotensin II antagonists, aldosterone blockers, heparin, low molecular weight heparin, other drugs or conditions known to cause hyperkalaemia or potassium supplements, a diet rich in potassium (including salt substitutes containing potassium), or other potassium sparing agents is not recommended as it may lead to severe hyperkalaemia. Hyperkalaemia may be fatal in patients with severe heart failure (New York Heart Association Class III–IV). Potassium and creatinine levels should be closely monitored one week after initiation or monthly for the first three months, then quarterly for a year, and then every six months when increasing the dose of spironolactone. Gynaecomastia may develop in association with the use of spironolactone. The development of gynaecomastia appears to be related to both dosage level and duration of therapy and is normally reversible when spironolactone is discontinued. Reversible hyperchloraemic metabolic acidosis, usually in association with hyperkalaemia, has been reported to occur in some patients with decompensated hepatic cirrhosis, even in the presence of normal renal function.

Contraindications

Spironolactone Viatris is contraindicated in acute renal insufficiency, significant impairment of renal function, anuria, Addison's disease or other conditions associated with hyperkalaemia, hyperkalaemia, pregnancy, hypersensitivity to spironolactone, and concomitant use of eplerenone.

Regulatory history

Spironolactone Viatris 25 mg and 100 mg tablet bottles were first registered on the Australian Register of Therapeutic Goods on 19 August 2020.