Spironolactone

How it works

It competitively antagonises aldosterone at the distal renal tubule, promoting sodium and water excretion while retaining potassium, and reduces aldosterone-mediated cardiac remodelling in heart failure.

Prescribing in practice

• Hyperkalaemia is the key hazard, especially in older people and those with renal impairment or on ACE inhibitors, ARBs or potassium supplements, so check renal function and potassium before and during treatment and avoid in significant renal impairment or pre-existing high potassium.
• It can cause gynaecomastia and breast tenderness, which may limit tolerability.
• Combine cautiously with other drugs affecting potassium or renal function, and review NSAID use.

Monitoring

Monitor renal function and serum potassium at baseline, shortly after starting and after dose changes, with closer review in older or renally impaired patients.

Counselling the patient

• Avoid potassium-containing salt substitutes and report muscle weakness or palpitations.
• Report breast swelling or tenderness, which can occur.

Evidence & guidelines

The RALES trial demonstrated that spironolactone reduced mortality in severe heart failure, and NICE recommends mineralocorticoid receptor antagonists as add-on therapy in HFrEF.