Trade names Midamor, others Routes ofadministration by mouth Molar mass 229.627 g/mol | AHFS/Drugs.com Monograph ATC code C03DB01 (WHO) CAS ID 2016-88-8 | |
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Pregnancycategory US: B (No risk in non-human studies) Legal status UK: POM (Prescription only)US: ℞-only | ||
Amiloride diuretics made simple
Amiloride, sold under the trade name Midamor among others, is a medication typically used with other medications to treat high blood pressure or swelling due to heart failure or cirrhosis of the liver. The medication it is used with often include a thiazide or loop diuretic. It is taken by mouth. Onset of action is about two hours and it lasts for about a day.
Contents
- Amiloride diuretics made simple
- Amiloride and triamterene
- Contraindications
- Adverse effects
- Structure
- Mechanism of action
- Society and culture
- Formulations and trade names
- References
Common side effects include high blood potassium, vomiting, loss of appetite, rash, and headache. The risk of high blood potassium is greater in those with kidney problems, diabetes, and those who are older. Amiloride is in the potassium-sparing diuretic family of medications. It works by increase the amount of sodium and decreasing the amount of potassium released by the distal tubule of the kidney.
Amiloride was developed in 1967. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. In the United States the wholesale price of a month of medication is about 20.10 USD. In the United Kingdom a month of medication costs the NHS about 24 pounds.
Amiloride and triamterene
Contraindications
Amiloride is contraindicated in people with Addison's disease, hyperkalaemia, hyponatremia and anuria.
Adverse effects
Structure
Amiloride's chemical structure contains a guanidinium group containing pyrazine derivative.
Mechanism of action
Amiloride works by directly blocking the epithelial sodium channel (ENaC) thereby inhibiting sodium reabsorption in the late distal convoluted tubules, connecting tubules, and collecting ducts in the nephron. This promotes the loss of sodium and water from the body, but without depleting potassium. The drug is often used in conjunction with a thiazide diuretic to counteract the potassium-sparing effect. Due to its potassium-sparing capacities, hyperkalemia can occur. The risk of developing hyperkalemia is high in patients who are also on ACE inhibitors, angiotensin II receptor antagonists, other potassium-sparing diuretics like spironolactone and eplerenone, or any potassium-containing supplements.
A fraction of the effects of amiloride is inhibition of cyclic GMP-gated cation channels in the inner medullary collecting duct.
Amiloride has a second action on the heart, blocking Na+/H+ exchangers sodium–hydrogen antiporter 1 or NHE-1. This minimizes re-perfusion injury in ischemic attacks.
Amiloride also blocks the Na+/H+ antiporter on the apical surface of the proximal tubule cells, in the nephron, abolishing more than 80% of the action of angiotensin II on the secretion of hydrogen ions in proximal tubule cells.
Amiloride was also tested as treatment of cystic fibrosis, but it was revealed inefficient in vivo due to its short time of action, therefore longer-acting epithelial sodium channel (ENaC) inhibitors may prove more effective, e.g. benzamil.
Acid-sensing ion channels (ASICs) are also sensitive to inhibition by amiloride. ASICs are involved in nociceptor responses to pH.
Society and culture
It is on the World Health Organization's List of Essential Medicines, the most important medication needed in a basic health system.
Amiloride is listed on the world anti-doping agency's list of banned substances, it is considered a masking agent.