Spironolactone

# Spironolactone ## Overview - **Classification**: Aldosterone antagonist, potassium-sparing diuretic. - **Mechanism**: Competitively binds to aldosterone receptors in the distal renal tubules, increasing Na+ and water excretion while conserving K+ and H+ ions. ## Primary Indications 1. **Heart Failure** - Reduced ejection fraction (NYHA Class III-IV). 2. **Edema** - Associated with cirrhosis (ascites) or nephrotic syndrome. 3. **Hypertension** - Often used as add-on therapy, especially for resistant HTN. 4. **Primary Hyperaldosteronism** - Diagnosis and long-term management. ## Adult Dosing ### Standard Dosing **Heart Failure (NYHA Class III-IV, reduced EF)** - **Dose**: Initiate with **12.5 mg** - **Frequency**: Once daily (PO) - **Route**: Oral - **Titration**: Increase to **25 mg** daily, then **50 mg** daily as tolerated, based on K+ and renal function. - **Maximum**: **50 mg** daily. **Edema (Cirrhosis, Nephrotic Syndrome)** - **Dose**: Initiate with **25-200 mg** - **Frequency**: Once daily or in 2-4 divided doses (PO) - **Route**: Oral - **Adjustment**: Adjust based on diuretic response, aiming for 0.5-1 kg weight loss/day. - **Maximum**: **400 mg** daily. **Hypertension** - **Dose**: Initiate with **25-50 mg** - **Frequency**: Once daily (PO) - **Route**: Oral - **Adjustment**: Adjust dose every 2 weeks as needed, up to **100 mg** daily. - **Maximum**: **100 mg** daily. **Primary Hyperaldosteronism** - **Dose**: **100-400 mg** - **Frequency**: Once daily or in divided doses (PO) - **Route**: Oral - **Maintenance**: **25-100 mg** daily once diagnosis confirmed. ### Dose Adjustments - **Renal Impairment**: - **CrCl < 30 mL/min**: **Contraindicated** due to high risk of hyperkalemia. - **CrCl 30-50 mL/min**: Use with **extreme caution**. Consider lower initial doses and frequent K+ monitoring. - **Hepatic Impairment**: Use with caution in severe impairment; monitor closely for electrolyte imbalances and hepatic encephalopathy. - **Elderly Patients**: Start at lower end of dosing range; increased risk of renal impairment and hyperkalemia. Monitor K+ and renal function closely. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **1-3 mg/kg** - **Frequency**: Once or twice daily (PO) - **Maximum**: Not well established, generally **3 mg/kg/day**. - **Special Notes**: Use with extreme caution. Close monitoring of electrolytes (especially K+) and renal function is critical. ### Infants (1-12 months) - **Dose**: **1-3 mg/kg** - **Frequency**: Once or twice daily (PO) - **Maximum**: **100 mg/day**. ### Children (1-12 years) - **Dose**: **1-3 mg/kg** - **Frequency**: Once or twice daily (PO) - **Maximum**: **100 mg/day**. ### Adolescents (13-18 years) - **Dose**: Approach adult dosing, typically **25-100 mg** daily depending on indication. - **Maximum**: Up to **400 mg/day** for edema; **50 mg/day** for heart failure. ## Safety Information ### Contraindications - **Absolute**: Hyperkalemia (serum K+ > 5.5 mEq/L) - **Absolute**: Anuria, acute renal insufficiency, or significant renal impairment (CrCl < 30 mL/min). - **Absolute**: Addison's disease or other conditions associated with hyperkalemia. - **Absolute**: Concurrent use with eplerenone. ### Common Adverse Effects - **Very Common (>10%)**: Hyperkalemia, gynecomastia (in males), breast pain (in females). - **Common (1-10%)**: Drowsiness, headache, GI upset (nausea, vomiting, diarrhea), impotence, menstrual irregularities, post-menopausal bleeding. - **Serious but Rare**: Agranulocytosis, Stevens-Johnson syndrome, toxic epidermal necrolysis, severe electrolyte imbalance leading to arrhythmias. ### Key Drug Interactions - **ACE Inhibitors/ARBs/Potassium Supplements/Other K-sparing diuretics**: Significantly increased risk of severe hyperkalemia. **Avoid concurrent use** or monitor K+ extremely closely. - **NSAIDs**: May attenuate diuretic/antihypertensive effects and increase risk of hyperkalemia and renal dysfunction. Monitor BP, renal function, K+. - **Digoxin**: May increase digoxin half-life, leading to elevated digoxin levels. Monitor digoxin levels. - **Lithium**: May reduce renal clearance of lithium, increasing risk of toxicity. Monitor lithium levels. - **Trimethoprim/Sulfamethoxazole (Bactrim)**: Synergistic hyperkalemic effect. **Avoid concurrent use** or monitor K+ extremely closely. ## Monitoring & Follow-up - **Before Treatment**: Baseline serum potassium, creatinine, BUN, eGFR. - **During Treatment**: - **Potassium & Renal Function**: 1 week after initiation/dose change, then monthly for 3 months, then quarterly or as clinically indicated. - **Blood Pressure**: Regularly, especially in hypertensive patients. - **Clinical Signs**: Monitor for symptoms of hyperkalemia (muscle weakness, fatigue, paresthesias, bradycardia, palpitations), gynecomastia, or other adverse effects. ## Clinical Pearls - 💡 **Tip 1**: Administer spironolactone with food to increase absorption and reduce gastrointestinal upset. - 💡 **Tip 2**: Counsel patients on symptoms of hyperkalemia (muscle weakness, fatigue) and to avoid potassium-rich foods or salt substitutes unless advised by their doctor. - 💡 **Tip 3**: Gynecomastia is a common, dose and duration-dependent side effect in men, which may not be fully reversible. Eplerenone is an alternative if this is intolerable. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.