Amiloride

Amiloride
Black Box Warning
Adult Indications & Dosage
Pediatric Indications & Dosage
Contraindications
Warnings & Precautions
Adverse Reactions
Drug Interactions
Use in Specific Populations
Administration & Monitoring
Overdosage
Pharmacology
Clinical Studies
How Supplied
Images
Patient Counseling Information
Precautions with Alcohol
Brand Names
Look-Alike Names

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Gerald Chi

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Black Box Warning

HYPERKALEMIA See full prescribing information for complete Boxed Warning. * Like other potassium-conserving agents, amiloride may cause hyperkalemia (serum potassium levels greater than 5.5 mEq per liter) which, if uncorrected, is potentially fatal. Hyperkalemia occurs commonly (about 10%) when amiloride is used without a kaliuretic diuretic. This incidence is greater in patients with renal impairment, diabetes mellitus (with or without recognized renal insufficiency), and in the elderly. When amiloride is used concomitantly with a thiazide diuretic in patients without these complications, the risk of hyperkalemia is reduced to about 1-2 percent. It is thus essential to monitor serum potassium levels carefully in any patient receiving amiloride, particularly when it is first introduced, at the time of diuretic dosage adjustments, and during any illness that could affect renal function.

Overview

Amiloride is a potassium-sparing diuretic that is FDA approved for the {{{indicationType}}} of congestive heart failure or hypertension adjunctive with thiazide diuretics or other kaliuretic-diuretic agents. There is a Black Box Warning for this drug as shown here. Common adverse reactions include rash, diarrhea, loss of appetite, nausea, vomiting, asthenia, cramp, dizziness, headache, cough, and dyspnea.

Adult Indications and Dosage

FDA-Labeled Indications and Dosage (Adult)

Congestive Heart Failure or Hypertension

• Dosing Information

• 5 mg tablet daily, should be added to the usual antihypertensive or diuretic dosage of a kaliuretic diuretic.

• The dosage may be increased to 10 mg per day, if necessary.
• More than two 5 mg tablets of amiloride daily usually are not needed, and there is little controlled experience with such doses.
• If persistent hypokalemia is documented with 10 mg, the dose can be increased to 15 mg, then 20 mg, with careful monitoring of electrolytes.

• In treating patients with congestive heart failure after an initial diuresis has been achieved, potassium loss may also decrease and the need for amiloride should be re-evaluated.

• Dosage adjustment may be necessary. Maintenance therapy may be on an intermittent basis.

• If it is necessary to use amiloride alone, the starting dosage should be one 5 mg tablet daily. This dosage may be increased to 10 mg per day, if necessary.

• More than two 5 mg tablets usually are not needed, and there is little controlled experience with such doses. If persistent hypokalemia is documented with 10 mg, the dose can be increased to 15 mg, then 20 mg, with careful monitoring of electrolytes.

Off-Label Use and Dosage (Adult)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Amiloride in adult patients.

Non–Guideline-Supported Use

Edema, Associated with Thiazolidinedione Use

• Dosing Information

• 10 mg once daily

Pediatric Indications and Dosage

FDA-Labeled Indications and Dosage (Pediatric)

Safety and effectiveness in pediatric patients have not been established.

Off-Label Use and Dosage (Pediatric)

Guideline-Supported Use

There is limited information regarding Off-Label Guideline-Supported Use of Amiloride in pediatric patients.

Non–Guideline-Supported Use

There is limited information regarding Off-Label Non–Guideline-Supported Use of Amiloride in pediatric patients.

Contraindications

• Hyperkalemia

• Amiloride should not be used in the presence of elevated serum potassium levels (greater than 5.5 mEq per liter).

• Antikaliuretic Therapy or Potassium Supplementation

• Amiloride should not be given to patients receiving other potassium-conserving agents, such as spironolactone or triamterene. Potassium supplementation in the form of medication, potassium-containing salt substitutes or a potassium-rich diet should not be used with amiloride except in severe and/or refractory cases of hypokalemia. Such concomitant therapy can be associated with rapid increases in serum potassium levels. If potassium supplementation is used, careful monitoring of the serum potassium level is necessary.

• Impaired Renal Function

• Anuria, acute or chronic renal insufficiency, and evidence of diabetic nephropathy are contraindications to the use of amiloride.
• Patients with evidence of renal functional impairment (blood urea nitrogen levels over 30 mg per 100 mL or serum creatinine levels over 1.5 mg per 100 mL) or diabetes mellitus should not receive the drug without careful, frequent and continuing monitoring of serum electrolytes, creatinine, and BUN levels. Potassium retention associated with the use of an antikaliuretic agent is accentuated in the presence of renal impairment and may result in the rapid development of hyperkalemia.

• Hypersensitivity

• Amiloride is contraindicated in patients who are hypersensitive to this product.

Warnings

HYPERKALEMIA See full prescribing information for complete Boxed Warning. * Like other potassium-conserving agents, amiloride may cause hyperkalemia (serum potassium levels greater than 5.5 mEq per liter) which, if uncorrected, is potentially fatal. Hyperkalemia occurs commonly (about 10%) when amiloride is used without a kaliuretic diuretic. This incidence is greater in patients with renal impairment, diabetes mellitus (with or without recognized renal insufficiency), and in the elderly. When amiloride is used concomitantly with a thiazide diuretic in patients without these complications, the risk of hyperkalemia is reduced to about 1-2 percent. It is thus essential to monitor serum potassium levels carefully in any patient receiving amiloride, particularly when it is first introduced, at the time of diuretic dosage adjustments, and during any illness that could affect renal function.

Hyperkalemia

• The risk of hyperkalemia may be increased when potassium-conserving agents, including amiloride, are administered concomitantly with an angiotensin-converting enzyme inhibitor, an angiotensin II receptor antagonist, cyclosporine or tacrolimus. Warning signs or symptoms of hyperkalemia include paresthesias, muscular weakness, fatigue, flaccid paralysis of the extremities, bradycardia, shock, and ECG abnormalities. Monitoring of the serum potassium level is essential because mild hyperkalemia is not usually associated with an abnormal ECG.

• When abnormal, the ECG in hyperkalemia is characterized primarily by tall, peaked T waves or elevations from previous tracings. There may also be lowering of the R wave and increased depth of the S wave, widening and even disappearance of the P wave, progressive widening of the QRS complex, prolongation of the PR interval, and ST depression.

Treatment of Hyperkalemia

• If hyperkalemia occurs in patients taking amilordie, the drug should be discontinued immediately.
• If the serum potassium level exceeds 6.5 mEq per liter, active measures should be taken to reduce it. Such measures include the intravenous administration of sodium bicarbonate solution or oral or parenteral glucose with a rapid-acting insulin preparation.
• If needed, a cation exchange resin such as sodium polystyrene sulfonate may be given orally or by enema.
• Patients with persistent hyperkalemia may require dialysis.

Diabetes Mellitus

• In diabetic patients, hyperkalemia has been reported with the use of all potassium-conserving diuretics, including amiloride, even in patients without evidence of diabetic nephropathy. Therefore, amiloride should be avoided, if possible, in diabetic patients and, if it is used, serum electrolytes and renal function must be monitored frequently.
• Amiloride should be discontinued at least three days before glucose tolerance testing.

Metabolic or Respiratory Acidosis

• Antikaliuretic therapy should be instituted only with caution in severely ill patients in whom respiratory acidosis or metabolic acidosis may occur, such as patients with cardiopulmonary disease or poorly controlled diabetes.
• If amiloride is given to these patients, frequent monitoring of acid-base balance is necessary. Shifts in acid-base balance alter the ratio of extracellular/intracellular potassium, and the development of acidosis may be associated with rapid increases in serum potassium levels.

Precautions

Electrolyte Imbalance and BUN Increases

• Hyponatremia and hypochloremia may occur when amiloride is used with other diuretics and increases in BUN levels have been reported.
• These increases usually have accompanied vigorous fluid elimination, especially when diuretic therapy was used in seriously ill patients, such as those who had hepatic cirrhosis with ascites and metabolic alkalosis, or those with resistant edema. Therefore, when amiloride is given with other diuretics to such patients, careful monitoring of serum electrolytes and BUN levels is important.
• In patients with pre-existing severe liver disease, hepatic encephalopathy, manifested by tremors, confusion, and coma, and increased jaundice, have been reported in association with diuretics, including amiloride HCl.

Carcinogenicity, Mutagenicity, Impairment of Fertility

• There was no evidence of a tumorigenic effect when amiloride HCl was administered for 92 weeks to mice at doses up to 10 mg/kg/day (25 times the maximum daily human dose). Amiloride HCl has also been administered for 104 weeks to male and female rats at doses up to 6 and 8 mg/kg/day (15 and 20 times the maximum daily dose for humans, respectively) and showed no evidence of carcinogenicity.

• Amiloride HCl was devoid of mutagenic activity in various strains of Salmonella typhimurium with or without a mammalian liver microsomal activation system (Ames test).

Adverse Reactions

Clinical Trials Experience

There is limited information regarding Clinical Trial Experience of Amiloride in the drug label.

Postmarketing Experience

• Amiloride is usually well tolerated and, except for hyperkalemia (serum potassium levels greater than 5.5 mEq per liter), significant adverse effects have been reported infrequently. Minor adverse reactions were reported relatively frequently (about 20%) but the relationship of many of the reports to amiloride HCl is uncertain and the overall frequency was similar in hydrochlorothiazide treated groups.

• Nausea/anorexia, abdominal pain, flatulence, and mild skin rash have been reported and probably are related to amiloride.

• Other adverse experiences that have been reported with amiloride are generally those known to be associated with diuresis, or with the underlying disease being treated.

• The adverse reactions for amiloride listed in the following table have been arranged into two groups:

• Group 1: Incidence greater than one percent
• Group 2: Incidence one percent or less

• The incidence for group 1 was determined from clinical studies conducted in the United States (837 patients treated with amiloride). The adverse effects listed in group 2 include reports from the same clinical studies and voluntary reports since marketing. The probability of a causal relationship exists between amiloride and these adverse reactions, some of which have been reported only rarely.

This image is provided by the National Library of Medicine.

• Causal Relationship Unknown

• Other reactions have been reported but occurred under circumstances where a causal relationship could not be established. However, in these rarely reported events, that possibility cannot be excluded. Therefore, these observations are listed to serve as alerting information to physicians.

• Activation of probable pre-existing peptic ulcer
• Aplastic anemia
• Neutropenia
• Abnormal liver function

Drug Interactions

• Angiotensin-converting enzyme inhibitor, angiotensin II receptor antagonist, Cyclosporine, or Tacrolimus

• When amiloride HCl is administered concomitantly with an angiotensin-converting enzyme inhibitor, an angiotensin II receptor antagonist, cyclosporine, or tacrolimus, the risk of hyperkalemia may be increased. Therefore, if concomitant use of these agents is indicated because of demonstrated hypokalemia, they should be used with caution and with frequent monitoring of serum potassium.

• Lithium

• Lithium generally should not be given with diuretics because they reduce its renal clearance and add a high risk of lithium toxicity. Read circulars for lithium preparations before use of such concomitant therapy.

• Non-steroidal anti-inflammatory agent

• In some patients, the administration of a non-steroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. Therefore, when amiloride and non-steroidal anti-inflammatory agents are used concomitantly, the patient should be observed closely to determine if the desired effect of the diuretic is obtained. Since indomethacin and potassium-sparing diuretics, including amiloride, may each be associated with increased serum potassium levels, the potential effects on potassium kinetics and renal function should be considered when these agents are administered concurrently.

Use in Specific Populations

Pregnancy

Pregnancy Category (FDA):

• Pregnancy Category B
• Teratogenicity studies with amiloride HCl in rabbits and mice given 20 and 25 times the maximum human dose, respectively, revealed no evidence of harm to the fetus, although studies showed that the drug crossed the placenta in modest amounts. Reproduction studies in rats at 20 times the expected maximum daily dose for humans showed no evidence of impaired fertility. At approximately 5 or more times the expected maximum daily dose for humans, some toxicity was seen in adult rats and rabbits and a decrease in rat pup growth and survival occurred.
• There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Pregnancy Category (AUS):

• Australian Drug Evaluation Committee (ADEC) Pregnancy Category C

Labor and Delivery

There is no FDA guidance on use of Amiloride during labor and delivery.

Nursing Mothers

• Studies in rats have shown that amiloride is excreted in milk in concentrations higher than those found in blood, but it is not known whether amiloride is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from amiloride, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Pediatric Use

• Safety and effectiveness in pediatric patients have not been established.

Geriatic Use

• Clinical studies of amiloride did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.

• This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

Gender

There is no FDA guidance on the use of Amiloride with respect to specific gender populations.

Race

There is no FDA guidance on the use of Amiloride with respect to specific racial populations.

Renal Impairment

There is no FDA guidance on the use of Amiloride in patients with renal impairment.

Hepatic Impairment

There is no FDA guidance on the use of Amiloride in patients with hepatic impairment.

Females of Reproductive Potential and Males

There is no FDA guidance on the use of Amiloride in women of reproductive potentials and males.

Immunocompromised Patients

There is no FDA guidance one the use of Amiloride in patients who are immunocompromised.

Administration and Monitoring

Administration

• Oral

• Amiloride should be administered with food.

Monitoring

Hyperkalemia

• It is essential to monitor serum potassium levels carefully in any patient receiving amiloride, particularly when it is first introduced, at the time of diuretic dosage adjustments, and during any illness that could affect [renal function]].

IV Compatibility

There is limited information regarding IV Compatibility of Amiloride in the drug label.

Overdosage

Acute Overdose

Signs and Symptoms

• The most likely signs and symptoms to be expected with overdosage are dehydration and electrolyte imbalance.
• No data are available in regard to overdosage in humans. The oral LD50 of amiloride hydrochloride (calculated as the base) is 56 mg/kg in mice and 36 to 85 mg/kg in rats, depending on the strain.

Management

• It is not known whether the drug is dialyzable.
• These can be treated by established procedures. Therapy with amiloride should be discontinued and the patient observed closely.
• There is no specific antidote. Emesis should be induced or gastric lavage performed. Treatment is symptomatic and supportive.
• If hyperkalemia occurs, active measures should be taken to reduce the serum potassium levels.

Chronic Overdose

There is limited information regarding Chronic Overdose of Amiloride in the drug label.

Pharmacology

Amiloride
Systematic (IUPAC) name
3,5-diamino-6-chloro-N-(diaminomethylene)pyrazine-2-carboxamide
Identifiers
CAS number	2016-88-8
ATC code	C03DB01
PubChem	16231
DrugBank	DB00594
Chemical data
Formula	Template:OrganicBox atomTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBox atomTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBoxTemplate:OrganicBox
Mol. mass	229.627 g/mol
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	Readily absorbed
Metabolism	none
Half life	6 to 9 hours
Excretion	unchanged in urine
Therapeutic considerations
Pregnancy cat.	B(US)
Legal status	[[Prescription drug|Template:Unicode-only]](US)
Routes	oral

Mechanism of Action

• Amiloride is a potassium-conserving (antikaliuretic) drug that possesses weak (compared with thiazide diuretics) natriuretic, diuretic, and antihypertensive activity. These effects have been partially additive to the effects of thiazide diuretics in some clinical studies. When administered with a thiazide or loop diuretic, amiloride has been shown to decrease the enhanced urinary excretion of magnesium which occurs when a thiazide or loop diuretic is used alone. Amiloride has potassium-conserving activity in patients receiving kaliuretic-diuretic agents.

• Amiloride is not an aldosterone antagonist and its effects are seen even in the absence of aldosterone.

Structure

• Amiloride HCl, an antikaliuretic-diuretic agent, is a pyrazine-carbonyl-guanidine that is unrelated chemically to other known antikaliuretic or diuretic agents. It is the salt of a moderately strong base (pKa 8.7). It is designated chemically as 3,5-diamino-6-chloro-N-(diaminomethylene) pyrazinecarboxamide monohydrochloride, dihydrate and has a molecular weight of 302.12. Its empirical formula is C6H8ClN7O•HCl•2H2O and its structural formula is:

This image is provided by the National Library of Medicine.

MIDAMOR1 (Amiloride HCl) is available for oral use as tablets containing 5 mg of anhydrous amiloride HCl. Each tablet contains the following inactive ingredients: calcium phosphate, D&C Yellow 10, iron oxide, lactose, magnesium stearate and starch.

Pharmacodynamics

• Amiloride exerts its potassium sparing effect through the inhibition of sodium reabsorption at the distal convoluted tubule, cortical collecting tubule and collecting duct; this decreases the net negative potential of the tubular lumen and reduces both potassium and hydrogen secretion and their subsequent excretion. This mechanism accounts in large part for the potassium sparing action of amiloride.

• Amiloride usually begins to act within 2 hours after an oral dose. Its effect on electrolyte excretion reaches a peak between 6 and 10 hours and lasts about 24 hours. Peak plasma levels are obtained in 3 to 4 hours and the plasma half-life varies from 6 to 9 hours. Effects on electrolytes increase with single doses of amiloride HCl up to approximately 15 mg.

Pharmacokinetics

• Amiloride HCl is not metabolized by the liver but is excreted unchanged by the kidneys. About 50 percent of a 20 mg dose of Amiloride is excreted in the urine and 40 percent in the stool within 72 hours. Amiloride has little effect on glomerular filtration rate or renal blood flow. Because amiloride HCl is not metabolized by the liver, drug accumulation is not anticipated in patients with hepatic dysfunction, but accumulation can occur if the hepatorenal syndrome develops.

Nonclinical Toxicology

There is limited information regarding Nonclinical Toxicology of Amiloride in the drug label.

Clinical Studies

There is limited information regarding Clinical Studies of Amiloride in the drug label.

How Supplied

• Tablets MIDAMOR, 5 mg, are yellow, diamond-shaped, compressed tablets, coded MSD 92 on one side and MIDAMOR on the other. They are supplied as follows:

NDC 0574-0291-01 bottles of 100.

Storage

• Protect from moisture, freezing and excessive heat.

Paddock Laboratories, Inc.

Minneapolis, MN 55427

Storage

There is limited information regarding Amiloride Storage in the drug label.

Images

Drug Images

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Package and Label Display Panel

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Patient Counseling Information

There is limited information regarding Amiloride Patient Counseling Information in the drug label.

Precautions with Alcohol

Alcohol-Amiloride interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

Brand Names

Midamor®

Look-Alike Drug Names

• aMILoride — amLODIPine

Drug Shortage Status

Price

References

The contents of this FDA label are provided by the National Library of Medicine.

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