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# Aldactone (spironolactone) ## Overview Spironolactone is a potassium-sparing diuretic and a competitive aldosterone receptor antagonist. It acts primarily in the distal renal tubules to promote sodium and water excretion while retaining potassium. ## Primary Indications * **Heart Failure (HFrEF):** Reduce morbidity/mortality in NYHA Class II–IV patients. * **Edematous conditions:** Ascites due to cirrhosis, nephrotic syndrome, or congestive heart failure. * **Primary Hyperaldosteronism:** Diagnosis and treatment. * **Essential Hypertension:** Often used as an add-on therapy (e.g., resistant hypertension). ## Adult Dosing * **Heart Failure:** Initial 12.5–25 mg once daily; titrate to maximum of 50 mg/day based on response and potassium levels. * **Edema (Cirrhosis/Nephrotic Syndrome):** 100 mg daily; dosing may range from 25–200 mg/day depending on clinical response. * **Hypertension:** 25–100 mg daily in one or two divided doses. * **Primary Hyperaldosteronism:** 100–400 mg daily prior to surgery; lowest effective dose for maintenance. ## Pediatric Dosing * **Heart Failure:** 1–3 mg/kg/day divided into 1–2 doses. * **Chronic Diuretic Therapy:** 1–3.3 mg/kg/day divided every 12–24 hours; maximum 200 mg/day (varies by institutional protocol). ## Dose Adjustments * **Renal Impairment:** Avoid if CrCl <30 mL/min due to high risk of severe hyperkalemia. Use with extreme caution and frequent monitoring if CrCl 30–50 mL/min. * **Hepatic Impairment:** No standard adjustment, but monitor for fluid/electrolyte shifts carefully. ## Contraindications * Anuria, acute renal insufficiency, or significant impairment of renal excretory function. * Hyperkalemia (serum potassium >5.0–5.5 mEq/L). * Addison’s disease. * Concomitant use of eplerenone. ## Adverse Effects * **Common:** Hyperkalemia, gynecomastia, breast tenderness, menstrual irregularities, erectile dysfunction, lethargy. * **Serious:** Severe hyperkalemia (cardiac arrhythmias), hyponatremia, metabolic acidosis, agranulocytosis (rare). ## Key Drug Interactions * **Potassium Supplements/Potassium-Sparing Diuretics:** Massive increase in hyperkalemia risk. * **ACE Inhibitors/ARBs:** Synergistic risk of hyperkalemia. * **NSAIDs:** May reduce natriuretic effect and increase risk of renal impairment/hyperkalemia. * **Lithium:** May reduce renal clearance of lithium, increasing toxicity risk. * **Digoxin:** May interfere with radioimmunoassay measurements and increase half-life. ## Monitoring * **Serum Potassium:** Before starting, within 1 week of initiation or dose change, and periodically thereafter. * **Renal Function (SCr/BUN):** Assess at baseline and regularly during therapy. * **Blood Pressure:** Monitor for hypotension. * **Fluid Status:** Weight/edema assessment. ## Clinical Pearls * **Hyperkalemia Management:** If potassium >5.0 mEq/L, reduce dose or discontinue. Do not initiate if potassium >5.0 mEq/L. * **Gynecomastia:** Dose- and duration-dependent. Consider switching to eplerenone if gynecomastia occurs, as eplerenone is more selective and lacks this side effect. * **Administration:** Administer consistently with or without food to minimize variability in absorption. *** **Educational Disclaimer:** This information is for educational purposes only and does not supersede local institutional protocols or professional clinical judgment. Always verify current prescribing information, contraindications, and dose adjustments using official drug monographs (e.g., Lexicomp, UpToDate) prior to prescribing.