Spironolactone

How it works

It competitively antagonises aldosterone at the distal renal tubule, promoting sodium and water excretion while conserving potassium.

Prescribing in practice

• Hyperkalaemia is the most important risk, particularly with renal impairment, ACE inhibitors, angiotensin receptor blockers or potassium supplements, so monitor potassium closely.
• It can cause gynaecomastia, breast tenderness and menstrual disturbance because of its anti-androgenic activity.
• Monitor renal function, as the combination of renal impairment and other renin-angiotensin agents increases the risk of dangerous hyperkalaemia and acute kidney injury.

Monitoring

Check renal function and serum potassium before starting and regularly during treatment, especially after dose changes or when combined with other agents affecting potassium.

Counselling the patient

• Avoid potassium-containing salt substitutes and supplements unless advised.
• Report breast swelling or tenderness, which may improve on stopping.
• Attend for the blood tests that check your kidneys and potassium.

Evidence & guidelines

Spironolactone improves outcomes in heart failure with reduced ejection fraction, as shown by the RALES trial and reflected in NICE guidance.