Amiloride/Hydrochlorothiazide

BRAND NAMES

• International: Moduretic
• Australia: Moduretic PI
• Canada: Moduretic
• Italy: Moduretic
• U.S.: Moduretic

STRUCTURE

• 

  Amiloride

• 

  Hydrochlorothiazide

MECHANISM OF ACTION

This is a combination of two diuretic agents with different but complementary mechanisms and sites of action, thereby providing additive diuretic and antihypertensive effects. Additionally, Amiloride helps to minimize the potassium loss characteristically induced by Hydrochlorothiazide.

Amiloride is potassium sparing diuretic that possesses weak (compared to the thiazide diuretics) natriuretic, diuretic and antihypertensive activity. 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 kidneys. This promotes the loss of sodium and water from the body, but without depleting potassium.

Hydrochlorothiazide is a thiazide diuretic, it acts on the distal convoluted tubule by inhibiting the sodium-chloride symporter. thus, it reduces NaCl reabsorption, leading to a retention of water in the urine. This symporter reabsorbs about 5% of filtered sodium. Hydrochlorothiazide enhance also Ca++ reabsorption in the distal convoluted tubule by inhibiting Na+ entry and thus enhancing the activity of Na+-Ca++ exchanger in the basolateral membrane of epithelial cells.

The onset of the diuretic action of Amiloride/Hydrochlorothiazide (Moduretic) is within 1 to 2 hours and this action appears to be sustained for approximately 24 hours.

INDICATIONS

Amiloride/Hydrochlorothiazide (Moduretic) is indicated alone or as an adjunct to other antihypertensive drugs in conditions such as:

• Edema of cardiac origin (heart failure);
• Hepatic cirrhosis with ascites and edema
• Hypertension

DOSAGE

Tablets containing 5 mg amiloride HCl and 50 mg hydrochlorothiazide.

Amiloride/Hydrochlorothiazide (Moduretic) should be administered with food.

HYPERTENSION
The usual dosage is one tablet given once a day or in divided doses. Some patients may require only half a tablet once a day.

EDEMA OF CARDIAC ORIGIN
Amiloride/Hydrochlorothiazide may be started at a dosage of one tablet a day. Dosage may be increased if necessary but must not exceed two tablets a day. The optimal dosage is determined by the diuretic response and the serum potassium level. Once an initial diuresis has been achieved, reduction in dosage should be attempted for maintenance therapy. Maintenance therapy may be on an intermittent basis.

HEPATIC CIRRHOSIS WITH ASCITES
Treatment should be initiated with a small dose (1 tablet once a day). If necessary, dosage may be increased gradually until there is effective diuresis. The dosage should not exceed two tablets per day. Maintenance doses may be lower than those required to initiate diuresis; therefore, reduction in the daily dose should be attempted when the patient’s weight is stabilized. Gradual weight reduction in cirrhotic patients is especially desirable to reduce the likelihood of untoward reactions associated with diuretic therapy

CONTRAINDICATIONS

• Hyperkalemia (defined as >5.5 mEq/l)
• Other concomitant antikaliuretic therapy or potassium supplementation
• Renal insufficiency (anuria, acute renal failure, severe progressive renal disease, and diabetic nephropathy)
• Hypersensitivity to any component of this product or other sulfonamide-derived drugs

SIDE EFFECTS

The most common side effects occuring in 3% to 8% of patients treated with Amiloride/Hydrochlorothiazide (Moduretic) are :

• Headache
• Weakness
• Nausea/anorexia
• Dizziness
• Rash

BIBLIOGRAPHY

• http://www.hypertensionmeds.com/packageinserts/moduretic.pdf