AMILORIDE

Indications

• Hypertension
• Congestive heart failure
• Edema associated with conditions such as nephrotic syndrome

Dosage

Children: Refer to the BNF for Children for specific dosing recommendations in paediatric patients.

Adults: Refer to the BNF for specific dosing recommendations based on the condition being treated.

Mechanism of action

Amiloride works by inhibiting sodium reabsorption in the distal convoluted tubules and collecting ducts of the kidneys. It binds to amiloride-sensitive sodium channels, resulting in increased sodium and water excretion while preventing potassium loss. Unlike aldosterone antagonists, amiloride's effects are evident even in the absence of aldosterone.

Pharmacodynamics

As a potassium-sparing diuretic, amiloride reduces blood pressure and aids in the management of fluid overload in patients with heart failure. It has a unique chemical structure that distinguishes it from other diuretics. Its potassium-sparing property can lead to hyperkalemia, particularly when used in conjunction with ACE inhibitors or other potassium-retaining medications.

Pharmacokinetics

Amiloride is administered orally and is absorbed well from the gastrointestinal tract. It has a half-life that allows for once-daily dosing in many cases. The drug is excreted primarily through the kidneys, and its pharmacokinetics can be affected by renal function. Adjustments may be necessary in patients with renal impairment.

Contra-indications

• Severe renal impairment
• Hyperkalemia
• Anuria

Adverse effects

• Hyperkalemia
• Hypotension
• Gastrointestinal disturbances
• Dizziness
• Headache

Interactions

• Increased risk of hyperkalemia with ACE inhibitors
• Increased risk of hyperkalemia with potassium supplements
• Increased risk of hyperkalemia with potassium-sparing diuretics like spironolactone
• May enhance the effects of other antihypertensive medications

Precautions

• Monitor renal function regularly
• Monitor serum potassium levels, particularly in high-risk patients
• Use cautiously in patients with hepatic impairment
• Caution in patients with a history of electrolyte imbalances

Pregnancy

Amiloride should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Amiloride is excreted in breast milk; caution should be exercised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat.

Formulations

• Tablets
• Oral solution

Indications

• Oedema
• Heart failure
• Hypertension
• Adjunct to thiazide or loop diuretics for potassium conservation

Dosage

Children: Child 1 month–11 years: 100–200 micrograms/kg twice daily; maximum 20 mg per day.

Adults: 5-10 mg once daily; dose may be adjusted based on clinical response.

Mechanism of action

Amiloride acts by inhibiting sodium reabsorption in the distal convoluted tubule and the collecting ducts of the kidneys, thereby promoting diuresis while conserving potassium.

Pharmacodynamics

As a potassium-sparing diuretic, amiloride enhances the excretion of sodium and water while reducing potassium loss, making it useful in conditions where hypokalemia may be a concern.

Pharmacokinetics

Amiloride is well absorbed from the gastrointestinal tract, with peak plasma concentrations reached within 1-2 hours. It is primarily excreted unchanged in the urine. The half-life is approximately 6-9 hours.

Contra-indications

• Addison’s disease
• anuria

Adverse effects

• Appetite decreased
• erectile dysfunction
• gastrointestinal discomfort
• hyperglycaemia
• rash

Interactions

• thiazide diuretics
• potassium-sparing diuretics

Precautions

• Diabetes mellitus

Pregnancy

Refer to BNF for specific guidance on use during pregnancy.

Breast-feeding

Refer to BNF for specific guidance on use during breastfeeding.

Storage

Store at room temperature, protected from light and moisture.

Formulations

• Amiloride hydrochloride 1 mg per 1 ml oral suspension
• Amiloride 5 mg/5 ml oral solution sugar-free
• Amiloride hydrochloride 5 mg tablets

Mechanism of action

Amiloride works by inhibiting sodium reabsorption in the distal convoluted tubules and collecting ducts in the kidneys by binding to the amiloride-sensitive sodium channels. This promotes the loss of sodium and water from the body, but without depleting potassium. 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. Amiloride is not an aldosterone antagonist and its effects are seen even in the absence of aldosterone.

Pharmacodynamics

Amiloride, an antikaliuretic-diuretic agent, is a pyrazine-carbonyl-guanidine that is unrelated chemically to other known antikaliuretic or diuretic agents. It is an antihypertensive, potassium-sparing diuretic that was first approved for use in 1967 and helps to treat hypertension and congestive heart failure. The drug is often used in conjunction with thiazide or loop diuretics. Due to its potassium-sparing capacities, hyperkalemia (high blood potassium levels) are occasionally observed in patients taking amiloride. The risk is high in concurrent use of ACE inhibitors or spironolactone. Patients are also advised not to use potassium-containing salt replacements.