Amiloride
Indication
Amiloride reduces potassium loss caused by other diuretics used in the management of hypertension or edema associated with congestive heart failure, hepatic cirrhosis, and hyperaldosteronism. Amiloride is usually used with other diuretics.
Mechanism of Action
Amiloride inhibits sodium-potassium ion exchange in the distal convoluted tubule by inhibiting cellular sodium transport mechanisms and inhibits hydrogen ion secretion; its diuretic activity is not dependent on aldosterone.
Dosing
Amiloride is only available for oral/enteral administration.
Children 6 to 20kg: 0.625mg/kg/day administered once daily (maximum dose, 10 mg/day)
Children heavier than 20kg and adults: 5 to 10 mg/day (maximum dose, 20mg/day)
In patients with renal impairment: reduce dose 50% for Cl10 to 50 mL/ min. Avoid use if ClCr is less than 10 mL/min
Pharmacokinetics
Amiloride has an onset of action of 2 hours and a duration of 24 hours. Oral bioavailability is 15 to 25%. The half-life in normal renal function is 6 to 9 hours and up to 144 hours in severe renal disease. Amiloride is eliminated in the urine and feces.
Monitoring parameters: serum potassium, blood pressure, blood urea nitrogen, Cr, fluid balance
Contraindications: anuria, hyperkalemia
Precautions/Adverse Effects
Use amiloride with caution with potassium supplements or other potassium-sparing diuretics; reduce dosage in patients with renal insufficiency; use cautiously in patients with diabetic nephropathy, hyponatremia, dehydration, electrolyte imbalance, or decreased hepatic function.
Adverse effects include hypotension, arrhythmias, hyperkalemia, hyponatremia, dehydration, hyperchloremic metabolic acidosis, nausea, vomiting, diarrhea, GI bleeding, liver function abnormalities, muscular weakness, paresthesias, neutropenia, aplastic anemia, headache, dizziness, confusion, insomnia, skin rash, and bladder spasms.
Poisoning Information
Symptoms include dehydration and electrolyte imbalances. Large doses can produce life-threatening hyperkalemia. Treatment is with I.V. glucose and insulin along with I.V. sodium bicarbonate. Dialysis may be necessary.
Drug-Drug Interactions
Amiloride increases serum potassium when used with potassium supplements, potassium-sparing diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, tacrolimus, and cyclosporine. Amiloride use decreases digoxin clearance, and decreases lithium clearance. NSAIDs decrease the effects of amiloride.
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