Amiloride
Pronunciation
(a MIL oh ride)
U.S. Brand Names
Midamor® [DSC]
Synonyms
Amiloride Hydrochloride
Generic Available
Yes
Canadian Brand Names
Midamor®
Use
Counteracts potassium loss induced by other diuretics in the treatment of hypertension or edematous conditions including CHF, hepatic cirrhosis, and hypoaldosteronism; usually used in conjunction with more potent diuretics such as thiazides or loop diuretics
Use - Unlabeled/Investigational
Investigational: Cystic fibrosis; reduction of lithium-induced polyuria
Pregnancy Risk Factor
B
Lactation
Excretion in breast milk unknown/contraindicated
Contraindications
Hypersensitivity to amiloride or any component of the formulation; presence of elevated serum potassium levels (>5.5 mEq/L); if patient is receiving other potassium-conserving agents (eg, spironolactone, triamterene) or potassium supplementation (medicine, potassium-containing salt substitutes, potassium-rich diet); anuria; acute or chronic renal insufficiency; evidence of diabetic nephropathy. Patients with evidence of renal impairment or diabetes mellitus should not receive this medicine without close, frequent monitoring of serum electrolytes and renal function.
Warnings/Precautions
May cause hyperkalemia (patients with renal impairment, diabetes and the elderly are at greatest risk). Should be stopped at least 3 days before glucose tolerance testing. Use caution in severely ill patients in whom respiratory or metabolic acidosis may occur.
Adverse Reactions
1% to 10%:
Central nervous system: Headache, fatigue, dizziness
Endocrine & metabolic: Hyperkalemia (up to 10%; risk reduced in patients receiving kaliuretic diuretics), hyperchloremic metabolic acidosis, dehydration, hyponatremia, gynecomastia
Gastrointestinal: Nausea, diarrhea, vomiting, abdominal pain, gas pain, appetite changes, constipation
Genitourinary: Impotence
Neuromuscular & skeletal: Muscle cramps, weakness
Respiratory: Cough, dyspnea
<1% (Limited to important or life-threatening): Orthostatic hypotension, arrhythmia, palpitation, chest pain, alopecia, GI bleeding, polyuria, bladder spasms, dysuria, jaundice, increased intraocular pressure, dyspnea
Overdosage/Toxicology
Clinical signs of toxicity are consistent with dehydration and electrolyte disturbance. Large amounts may result in life-threatening hyperkalemia (>6.5 mEq/L). This can be treated with I.V. glucose (dextrose 25% in water), rapid-acting insulin, concurrent I.V. sodium bicarbonate, and (if needed) Kayexalate® oral or rectal solution in sorbitol. Persistent hyperkalemia may require dialysis.
Drug Interactions
Amoxicillin's absorption may be reduced; avoid concurrent use or observe for clinical response.
ACE inhibitors or angiotensin receptor antagonists can cause hyperkalemia, especially in patients with renal impairment, potassium-rich diets, or on other drugs causing hyperkalemia; avoid concurrent use or monitor closely.
Cyclosporine or tacrolimus: Risk of hyperkalemia may be increased by concurrent therapy.
NSAIDs: May decrease the effect of diuretics.
Potassium supplements may further increase potassium retention and cause hyperkalemia; avoid concurrent use.
Quinidine and amiloride together may increase risk of malignant arrhythmias; avoid concurrent use.
Ethanol/Nutrition/Herb Interactions
Food: Hyperkalemia may result if amiloride is taken with potassium-containing foods.
Mechanism of Action
Interferes with potassium/sodium exchange (active transport) in the distal tubule, cortical collecting tubule and collecting duct by inhibiting sodium, potassium-ATPase; decreases calcium excretion; increases magnesium loss
Pharmacodynamics/Kinetics
Onset of action: 2 hours
Duration: 24 hours
Absorption: ~15% to 25%
Distribution: Vd: 350-380 L
Protein binding: 23%
Metabolism: No active metabolites
Half-life elimination: Normal renal function: 6-9 hours; End-stage renal disease: 8-144 hours
Time to peak, serum: 6-10 hours
Excretion: Urine and feces (equal amounts as unchanged drug)
Dosage
Oral:
Children: Although safety and efficacy in children have not been established by the FDA, a dosage of 0.625 mg/kg/day has been used in children weighing 6-20 kg.
Adults: 5-10 mg/day (up to 20 mg)
Hypertension (JNC 7): 5-10 mg/day in 1-2 divided doses
Elderly: Initial: 5 mg once daily or every other day
Dosing adjustment in renal impairment:
Clcr 10-50 mL/minute: Administer at 50% of normal dose.
Clcr<10 mL/minute: Avoid use.
Administration
Administer with food or meals to avoid GI upset.
Monitoring Parameters
I & O, daily weights, blood pressure, serum electrolytes, renal function
Test Interactions
Increased potassium (S)
Dietary Considerations
Take with food or meals to avoid GI upset. Do not use salt substitutes or low salt milk without checking with your healthcare provider, too much potassium can be as harmful as too little.
Patient Education
Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy unless approved by prescriber. Take as directed, preferably early in day with food. Do not increase dietary intake of potassium unless instructed by prescriber (too much potassium can be as harmful as too little). May cause dizziness or fatigue (use caution when driving or engaging in tasks that require alertness until response to drug is known); constipation (increased exercise, fluids, fruit, and fiber may help); impotence (reversible); or loss of hair (rare). Report muscle cramping or weakness, unresolved nausea or vomiting, palpitations, or respiratory difficulty.
Breast-feeding precaution:
Do not breast-feed.
Additional Information
Medication should be discontinued if potassium level exceeds 6.5 mEq/L. Combined with hydrochlorothiazide as Moduretic®. Amiloride is considered an alternative to triamterene or spironolactone.
Anesthesia and Critical Care Concerns/Other Considerations
Medication should be discontinued if hyperkalemia develops. Amiloride may cause hyperkalemia, the ECG manifestations may include peaked T waves, QRS prolongation, and cardiac conduction abnormalities.
Cardiovascular Considerations
Amiloride may cause hyperkalemia, the ECG manifestations of which include peaked T waves, QRS prolongation, and cardiac conduction abnormalities.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
May cause drowsiness; rarely may cause insomnia and depression
Mental Health: Effects on Psychiatric Treatment
May cause impotence and orthostatic hypotension which may be exacerbated by psychotropics; effective agent for the treatment of lithium induced diabetes insipidus
Dosage Forms
Tablet, as hydrochloride: 5 mg
References
Chobanian AV, Bakris GL, Black HR, et al, "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report,"
JAMA
, 2003, 289(19):2560-71.
Jaffey L and Martin A, "Malignant Hyperkalemia After Amiloride/Hydrochlorothiazide Treatment,"
Lancet
, 1981, 1(8232):1272.
Kleyman TR and Cragoe EJ Jr, "The Mechanism of Action of Amiloride,"
Semin Nephrol
, 1988, 8(3):242-8.
Wang L, Sheldon RS, Mitchell LB, et al, "Amiloride-Quinidine Interaction: Adverse Outcomes,"
Clin Pharmacol Ther
, 1994, 56(6 Pt 1):659-67.
International Brand Names
Alverix® (CY); Amiclaran® (CZ, SK); Amilamont® (GB); Amiloferm Mite® (SE); Amiloferm® (SE); Amiloride Alpharma Aps® (SG); Amiloride® (GB); Amilorid NM Pharma® (SE); Amiride® (IL); Amitrid® (FI); Apo-Amilzide® (CZ); Berkamil® (IE); Kaluril® (AU); Loradur® (AT, CZ); Medamor® (FI); Midamor® (AT, AU, CA, CH, GB, HK, NZ, SE); Modamide® (FR); Nirulid® (DK); Pandiuren® (AR)
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