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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 inhibit sodium reabsorption and potassium excretion.
## Primary Indications
* Heart failure (NYHA Class II–IV, with reduced ejection fraction).
* Primary hyperaldosteronism (diagnosis and long-term management).
* Edema associated with hepatic cirrhosis or nephrotic syndrome.
* Essential hypertension (often as add-on therapy).
## Adult Dosing
* **Heart Failure:** Initial 12.5–25 mg once daily. Target dose: 25 mg once daily.
* **Hypertension:** 25–100 mg/day in single or divided doses.
* **Primary Hyperaldosteronism:** 100–400 mg/day until surgery; use lowest effective dose for long-term maintenance.
* **Edema (Cirrhosis/Nephrosis):** 25–200 mg/day; adjust based on response.
## Pediatric Dosing
* **Hypertension/Diuretic (Off-label):** Initial 1–3 mg/kg/day divided every 12–24 hours. Maximum: 3.3 mg/kg/day or 100 mg/day.
* **Heart Failure (Off-label):** 1–2 mg/kg/day once daily. Maximum: 25 mg/day.
## Dose Adjustments
* **Renal Impairment:** Avoid or exercise extreme caution if eGFR <30 mL/min/1.73m². Dose reduction may be required; withhold if serum potassium increases significantly.
* **Hepatic Impairment:** Reduce dose in patients with severe hepatic impairment; monitor closely for fluid/electrolyte imbalance.
## Contraindications
* Hyperkalemia (K >5.0–5.5 mEq/L).
* Addison’s disease.
* Concomitant use with eplerenone or potassium supplements/potassium-sparing diuretics.
* Anuria or acute renal insufficiency.
## Adverse Effects
* **Common:** Hyperkalemia, gynecomastia, breast tenderness, dizziness, headache.
* **Serious:** Severe arrhythmias (secondary to hyperkalemia), metabolic acidosis, gastric bleeding, hyponatremia.
## Key Drug Interactions
* **Potassium-sparing diuretics/supplements:** High risk of lethal hyperkalemia.
* **ACE inhibitors/ARBs/Aliskiren:** Increased risk of hyperkalemia.
* **Lithium:** May reduce lithium clearance, increasing toxicity risk.
* **NSAIDs:** May attenuate diuretic effect and increase risk of hyperkalemia and renal failure.
* **Digoxin:** May increase serum digoxin levels.
## Monitoring
* **Serum Potassium:** Initial periodic monitoring, then monthly for the first 3 months and every 3–6 months thereafter.
* **Renal Function:** Monitor BUN and Creatinine baseline and after initiation or dose changes.
* **Blood Pressure:** Monitor for orthostatic hypotension.
## Clinical Pearls
* **Take with food:** Administration with food may increase the bioavailability of spironolactone.
* **Gynecomastia:** This dose-dependent effect is reversible upon discontinuation; it is less common with lower doses (e.g., 25 mg in heart failure) but can be persistent.
* **Half-life:** The active metabolite (canrenone) has a long half-life, meaning effects do not cease immediately upon drug discontinuation.
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*Disclaimer: This information is for educational purposes and does not replace professional clinical judgment. Always verify current prescribing information, institutional protocols, and patient-specific factors before administration.*
