Spironolactone

What is Spironolactone?

Spironolactone is a potassium-sparing diuretic that works by blocking aldosterone receptors in the kidneys. It is primarily used to treat fluid retention, high blood pressure, and certain hormonal conditions. Unlike other diuretics, spironolactone helps the body eliminate excess sodium and water while retaining potassium.

Uses

Spironolactone has several approved medical uses:

• Heart failure: Used as an add-on treatment to reduce fluid buildup and improve survival rates in patients with severe heart failure
• High blood pressure: Helps lower blood pressure by reducing fluid volume and blocking aldosterone effects on blood vessels
• Edema: Treats fluid retention associated with liver disease, kidney disorders, or congestive heart failure
• Primary aldosteronism: Manages conditions where the body produces too much aldosterone hormone
• Hirsutism and acne: Used off-label in women to treat excess hair growth and hormonal acne by blocking androgen receptors

How it works

Spironolactone blocks aldosterone receptors in the distal tubules of the kidneys, preventing sodium reabsorption and potassium loss. This mechanism causes the body to excrete excess sodium and water through urine while conserving potassium. The drug also has anti-androgen properties, which explains its effectiveness in treating certain hormonal conditions in women.

Side effects

Common side effects include:

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• Elevated potassium levels (hyperkalemia)
• Dizziness or lightheadedness
• Headache
• Nausea and vomiting
• Diarrhea
• Drowsiness or fatigue
• Irregular menstrual periods in women
• Breast tenderness or enlargement

Serious side effects requiring immediate medical attention:

• Severe hyperkalemia (muscle weakness, irregular heartbeat)
• Signs of electrolyte imbalance (confusion, muscle cramps, severe weakness)
• Kidney problems (decreased urination, swelling)
• Severe allergic reactions (rash, difficulty breathing, swelling of face or throat)
• Liver problems (yellowing of skin or eyes, dark urine)

Warnings and precautions

• Kidney disease: Patients with severe kidney impairment should avoid spironolactone due to increased risk of dangerous potassium buildup
• Hyperkalemia risk: Regular monitoring of potassium levels is essential, especially when starting treatment or adjusting doses
• Pregnancy: Generally avoided during pregnancy due to potential hormonal effects on fetal development; classified as pregnancy category C
• Addison’s disease: Contraindicated in patients with this condition due to already elevated potassium levels
• Elderly patients: Require closer monitoring due to increased sensitivity to electrolyte changes and higher risk of kidney problems

Interactions

Spironolactone has several important drug interactions:

• ACE inhibitors and ARBs: Increase risk of hyperkalemia when combined with spironolactone
• Potassium supplements: Can lead to dangerous potassium levels and should generally be avoided
• NSAIDs: May reduce spironolactone’s effectiveness and increase kidney damage risk
• Lithium: Spironolactone can increase lithium levels, potentially causing toxicity
• Digoxin: May increase digoxin levels and risk of side effects
• Salt substitutes: Many contain potassium and can contribute to hyperkalemia
• Trimethoprim-sulfamethoxazole: Increases potassium retention risk
• Heparin: Long-term use with spironolactone may increase potassium levels

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Dosage

Typical adult dosages vary by condition:

• Heart failure: Usually 25-50 mg once daily, may be increased to 25 mg twice daily
• High blood pressure: 50-100 mg daily, given as single dose or divided doses
• Edema: 25-200 mg daily, depending on response and underlying condition
• Primary aldosteronism: 100-400 mg daily for diagnosis; 100-400 mg daily for long-term management

Dosages should always be individualized and determined by a healthcare provider based on the patient’s specific condition, kidney function, and response to treatment. Regular monitoring of electrolytes and kidney function is essential during treatment.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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