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# Spironolactone (Aldactone)
## Overview
Spironolactone is a potassium-sparing diuretic and a competitive aldosterone antagonist. It acts in the distal tubules and collecting ducts of the nephron to inhibit sodium and water reabsorption, while promoting potassium retention.
## Primary Indications
* Heart failure (NYHA class II-IV) with reduced ejection fraction
* Hypertension
* Edema associated with cirrhosis or nephrotic syndrome
* Primary hyperaldosteronism
## Adult Dosing
* **Heart Failure:** Start at 25 mg once daily. May increase to 50 mg once daily after 4 weeks if a response is not achieved. Further increase to a maximum of 100 mg once daily if necessary.
* **Hypertension:** Start at 25-100 mg once daily. May be combined with other antihypertensives. Maximum dose typically 400 mg/day, but often lower doses are effective.
* **Edema (Cirrhosis/Nephrotic Syndrome):** Start at 25-100 mg once daily. Dose may be adjusted based on response. Maximum dose typically 400 mg/day.
* **Primary Hyperaldosteronism:** Preoperative: 100-400 mg/day. Long-term maintenance: Dose adjusted to maintain normal serum electrolytes.
## Pediatric Dosing
Dosing in pediatric patients is not well-established and should be individualized based on clinical response and patient factors. Typical starting doses range from 1-3 mg/kg/day divided into 1-2 doses. The maximum dose is generally 100 mg/day, but doses up to 200 mg/day have been used in some cases.
## Dose Adjustments
* **Renal Impairment:** Use with caution in patients with significant renal impairment. Monitor potassium closely.
* **Hepatic Impairment:** Use with caution in patients with hepatic impairment.
## Contraindications
* Anuria
* Acute renal insufficiency
* Significant impairment of renal excretion
* Hyperkalemia
* Addison's disease
* Known hypersensitivity to spironolactone
## Adverse Effects
* **Common:** Hyperkalemia, hyponatremia, dizziness, headache, gastrointestinal disturbances (nausea, vomiting, diarrhea), gynecomastia (in males), menstrual irregularities (in females).
* **Less Common:** Lethargy, confusion, rash, urticaria, deepening of voice, breast tenderness, erectile dysfunction.
## Key Drug Interactions
* **ACE inhibitors, ARBs, other potassium-sparing diuretics, potassium supplements, NSAIDs:** Increased risk of hyperkalemia.
* **Corticosteroids:** May reduce efficacy of spironolactone and increase risk of hyponatremia.
* **Digoxin:** Spironolactone can increase digoxin levels.
* **Lithium:** Spironolactone may decrease lithium clearance, leading to lithium toxicity.
* **Cholestyramine:** Increased risk of hyperkalemia.
## Monitoring
* Serum electrolytes (especially potassium and sodium)
* Renal function (serum creatinine, BUN)
* Blood pressure
* For patients with heart failure, monitor for signs of worsening heart failure and fluid overload.
* For patients with cirrhosis, monitor for fluid accumulation.
## Clinical Pearls
* Administer with food to improve absorption and reduce gastrointestinal upset.
* Due to its hormonal effects, gynecomastia and menstrual irregularities can occur.
* Patients with impaired renal function or those taking other medications that increase potassium levels are at higher risk for hyperkalemia.
* Consider switching to eplerenone for patients experiencing significant gynecomastia or other hormonal side effects, although eplerenone is generally more expensive.
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*This information is intended for healthcare professionals. Always consult the current prescribing information and relevant guidelines for complete and up-to-date details.*
