Spironolactone

Key points

• Spironolactone is a mineralocorticoid-receptor antagonist (aldosterone antagonist) acting in the distal nephron/collecting duct to reduce sodium reabsorption and potassium excretion.
• Ascites due to cirrhosis: spironolactone is an important diuretic because cirrhosis causes secondary hyperaldosteronism; doses can be substantially higher than those used for hypertension or heart failure and require monitoring.
• Resistant hypertension: NICE recommends considering low-dose spironolactone as step 4 treatment when serum potassium is 4.5 mmol/L or less , with particular caution in reduced eGFR and monitoring of renal function/electrolytes.
• Heart failure with reduced ejection fraction: an MRA such as spironolactone is part of guideline-directed therapy when appropriate, with monitoring for hyperkalaemia and renal dysfunction.
• Nephrotic syndrome: spironolactone is not a universal primary treatment for nephrotic syndrome; it may be used as part of oedema/proteinuria management in selected patients with specialist oversight.
• Primary hyperaldosteronism (Conn syndrome) is a recognised indication for mineralocorticoid-receptor antagonism, particularly when surgery is not appropriate or while awaiting definitive management.
• MRCP discriminator: resistant hypertension + K⁺ ≤4.5 mmol/L → consider low-dose spironolactone; HFrEF → MRA; cirrhotic ascites → spironolactone is a key diuretic.
• Classic adverse effects: hyperkalaemia, renal impairment, gynaecomastia and menstrual disturbances.