Amiloride

# Amiloride ## Overview - **Classification**: Potassium-sparing diuretic - **Mechanism**: Blocks Na+ channels (ENaC) in the late distal convoluted tubule and collecting duct, reducing Na+ reabsorption and K+ excretion. This conserves potassium. ## Primary Indications 1. **Hypertension/CHF**: Adjunct to thiazide or loop diuretics to prevent hypokalemia. 2. **Liddle's Syndrome**: Treatment of this rare genetic form of hypertension. ## Adult Dosing ### Standard Dosing **Adjunctive Therapy with Thiazide/Loop Diuretics (Hypertension/CHF)** - **Dose**: Initially **5 mg** - **Frequency**: Once daily - **Route**: Oral - **Maximum Dose**: **20 mg/day** (may be given as 10 mg once daily or 5 mg twice daily) - **Special Considerations**: Titrate based on serum potassium levels and diuretic response. **Liddle's Syndrome** - **Dose**: **5 mg** initially - **Frequency**: Once or twice daily - **Route**: Oral - **Maximum Dose**: Up to **20 mg/day** - **Special Considerations**: Titrate carefully based on blood pressure and potassium levels. ### Dose Adjustments - **Renal Impairment**: - **CrCl 30-50 mL/min**: Use with caution, start lower dose (e.g., **2.5 mg/day**), monitor K+ closely. - **CrCl <30 mL/min**: **Contraindicated** due to severe hyperkalemia risk. - **Hepatic Impairment**: Use with caution; monitor for electrolyte imbalances, especially in severe cirrhosis (risk of hepatic encephalopathy). - **Elderly Patients**: Increased risk of hyperkalemia. Start with lower doses (e.g., **2.5 mg/day**) and monitor electrolytes frequently. ## Pediatric Dosing *Note: Amiloride use in pediatrics is often off-label and requires careful monitoring due to limited data.* ### Neonates (0-28 days) - **Dose**: Limited data, typically **0.2-0.4 mg/kg** - **Frequency**: Once daily - **Maximum**: **10 mg/day** - **Special Notes**: Only for specific conditions (e.g., Liddle's syndrome, nephrogenic DI). Requires close electrolyte monitoring. Tablets may need to be crushed or compounded. ### Infants (1-12 months) - **Dose**: **0.2-0.4 mg/kg** - **Frequency**: Once daily - **Maximum**: **10 mg/day** - **Special Notes**: Monitor closely for hyperkalemia and renal function. ### Children (1-12 years) - **Dose**: **0.2-0.4 mg/kg** - **Frequency**: Once daily - **Maximum**: **20 mg/day** - **Special Notes**: For specific indications only. Start low and titrate based on response and electrolyte levels. ### Adolescents (13-18 years) - **Dose**: Similar to adult dosing, start at **5 mg** - **Frequency**: Once daily - **Maximum**: **20 mg/day** - **Special Notes**: Closely monitor electrolytes and renal function. ## Safety Information ### Contraindications - **Absolute**: Hyperkalemia (>5.5 mEq/L) - **Absolute**: Anuria, acute renal failure, severe renal impairment (CrCl <30 mL/min) - **Absolute**: Concomitant use with other potassium-sparing diuretics (e.g., spironolactone, triamterene) - **Absolute**: Concomitant use with potassium supplements - **Absolute**: Hypersensitivity to amiloride ### Common Adverse Effects - **Very Common (>10%)**: Hyperkalemia (especially with impaired renal function, diabetes, elderly) - **Common (1-10%)**: Headache, nausea, diarrhea, abdominal pain, weakness, fatigue, dizziness, rash. - **Serious but Rare**: Metabolic acidosis, cardiac arrhythmias (due to hyperkalemia), blood dyscrasias. ### Key Drug Interactions - **Potassium Supplements/Other K-sparing Diuretics**: Significant risk of severe hyperkalemia. **AVOID CONCOMITANT USE**. - **ACE Inhibitors/ARBs**: Increased risk of hyperkalemia. Monitor serum potassium closely, especially when initiating or adjusting doses. - **NSAIDs**: May reduce diuretic and antihypertensive effects; can increase risk of hyperkalemia and renal dysfunction. Use with caution. - **Lithium**: Decreases lithium renal clearance, increasing risk of lithium toxicity. Monitor lithium levels. - **Digoxin**: May increase digoxin levels; monitor digoxin. ## Monitoring & Follow-up - **Before Treatment**: Baseline serum potassium, creatinine, BUN, blood pressure. - **During Treatment**: - Serum **potassium** (especially during first few weeks, after dose changes, and periodically thereafter - e.g., monthly for 3 months, then quarterly). - Serum creatinine, BUN, blood pressure. - Glucose (in diabetic patients). - **Clinical Signs**: Monitor for signs of hyperkalemia (muscle weakness, fatigue, bradycardia, confusion, paresthesias). ## Clinical Pearls - 💡 **Timing**: Often given with a thiazide or loop diuretic to counteract potassium loss. - 💡 **Food**: Take with food or milk to reduce GI upset. - 💡 **Potassium Intake**: Counsel patients to **avoid potassium supplements, salt substitutes** (often contain potassium chloride), and potassium-rich foods. - 💡 **Hyperkalemia Risk**: Highest risk in patients with renal impairment, diabetes, and the elderly. Monitor K+ closely. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.