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# Spironolactone (Aldactone)
## Overview
Spironolactone is a potassium-sparing diuretic and a competitive aldosterone antagonist. It inhibits the effects of aldosterone in the distal tubules and collecting ducts of the nephron, leading to increased sodium and water excretion and potassium retention.
## Primary Indications
* Heart failure (NYHA class II-IV) with reduced ejection fraction
* Edema associated with liver cirrhosis
* Edema associated with nephrotic syndrome
* Essential hypertension
* Primary hyperaldosteronism
* Hirsutism in women
## Adult Dosing
* **Heart Failure:** Start at 25 mg orally once daily. May increase to 50 mg orally once daily. Maximum dose is 100 mg orally once daily.
* **Cirrhosis with Ascites:** Start at 100 mg orally once daily. May range from 25-200 mg orally once daily.
* **Nephrotic Syndrome:** Start at 25-100 mg orally once daily.
* **Hypertension:** Start at 25-100 mg orally once daily, often in combination with other antihypertensives. Maximum dose is 200 mg orally once daily.
* **Primary Hyperaldosteronism:** 100-400 mg orally once daily.
* **Hirsutism:** 100-200 mg orally once daily.
## Pediatric Dosing
* **Diuretic/Edema:** 1.5 to 3 mg/kg/day orally divided into 2 to 4 doses. Maximum: 3.3 mg/kg/day.
* **Hypertension:** 1.5 to 3 mg/kg/day orally divided into 2 to 4 doses.
* **Specific indications and doses may vary; consult pediatric guidelines.** There is less established pediatric data for some indications.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Monitor potassium closely. Avoid if serum creatinine is > 2.5 mg/dL or if in-dwelling urinary catheter is in place. In patients with heart failure, consider dose reduction or discontinuation if GFR < 30 mL/min/1.73m$^2$.
* **Hepatic Impairment:** Use with caution; may precipitate hepatic coma.
## Contraindications
* Anuria
* Acute renal insufficiency
* Significant and progressive renal impairment
* Hyperkalemia (serum potassium > 5.5 mEq/L)
* Addison's disease
* Concomitant use with eplerenone
## Adverse Effects
* **Common:** Hyperkalemia, hyponatremia, dizziness, headache, gastrointestinal upset (nausea, vomiting, diarrhea), gynecomastia, menstrual irregularities.
* **Serious:** Severe hyperkalemia, hypotension, Stevens-Johnson syndrome, toxic epidermal necrolysis, rhabdomyolysis.
## Key Drug Interactions
* **ACE inhibitors, ARBs, NSAIDs, potassium supplements, other potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **Digoxin:** Spironolactone may increase digoxin levels.
* **Lithium:** Spironolactone may decrease lithium clearance, increasing lithium toxicity risk.
* **Cholestyramine:** May increase risk of hyperkalemia.
* **Corticosteroids:** May increase risk of hyponatremia.
## Monitoring
* **Serum electrolytes (potassium, sodium)** at baseline and periodically. Frequency depends on indication, renal function, and concomitant medications. In heart failure, typically at 1 week, 1 month, and every few months thereafter.
* **Renal function (serum creatinine, BUN)** at baseline and periodically.
* **Blood pressure** regularly.
* **For hirsutism:** Monitor for efficacy and adverse effects.
## Clinical Pearls
* Administer with food to improve absorption.
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