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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:

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

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)

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.

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