Spironolactone is a potassium-sparing diuretic that acts as a competitive antagonist of aldosterone at mineralocorticoid receptors in the distal renal tubules. By blocking aldosterone, it reduces sodium and water reabsorption while conserving potassium. This mechanism makes it valuable in conditions characterized by volume overload, hypertension, and states of hyperaldosteronism. Unlike loop or thiazide diuretics, spironolactone provides a milder diuresis but has the unique benefit of countering potassium loss, which is clinically significant in patients prone to hypokalaemia. Introduced in the late 1950s, it has since become a cornerstone in the management of heart failure with reduced ejection fraction (HFrEF) and resistant hypertension. Additionally, its anti-androgenic properties have broadened its use in dermatology and endocrinology for conditions such as hirsutism, acne, and polycystic ovary syndrome (PCOS).
Pharmacologically, spironolactone is metabolized into active metabolites (including canrenone) that prolong its therapeutic effect. Its onset is gradual, typically requiring several days of continuous therapy for full effect, distinguishing it from more immediate diuretics. Clinicians must be mindful of its potential to cause hyperkalaemia, especially in patients with impaired renal function or those on concurrent potassium-retaining therapies.
Spironolactone has a broad international footprint, marketed under numerous brand names across Europe, the Americas, Asia, and Africa. Its versatility, cost-effectiveness, and evidence base in prolonging survival in advanced heart failure (RALES trial) have cemented its role in modern therapeutics.
Therapeutic effect on oedema and blood pressure may take several days. Routine monitoring of serum electrolytes and renal function is mandatory, especially early in therapy.
Side effects are dose-dependent. Dermatological patients on high doses for acne/hirsutism may experience more pronounced hormonal effects.
Patients must be educated about dietary potassium intake (avoid salt substitutes containing potassium chloride) and the need for regular blood tests.
Patients should provide a full list of medications, including OTC drugs and supplements, to their healthcare providers.
Overdose: May result in hyperkalaemia, hyponatraemia, dehydration, hypotension. Management includes supportive care, intravenous fluids, correction of electrolytes, and ECG monitoring. Severe hyperkalaemia may require IV calcium, insulin with glucose, and dialysis.
Accidental double dose: May cause mild dizziness or nausea; monitor and contact a clinician if symptoms develop. Avoid taking extra tablets to compensate for missed doses.
Missed dose: Take when remembered unless close to the next scheduled dose. Do not double up. Regularity is more important than occasional missed doses.
The information provided on this website is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor, pharmacist, or other qualified health provider with any questions you may have regarding a medical condition or medication. Do not disregard professional medical advice or delay seeking it because of something you have read here. We do not take responsibility for any loss, damage, or injury caused by this information.