AMILORIDE HYDROCHLORIDE

AMILORIDE HYDROCHLORIDe
(a-mill'oh-ride)
Midamor
Classifications: diuretic, potassium-sparing;
Therapeutic: diuretic, potassium-sparing
; antihypertensive
Prototype: Spironolactone
Pregnancy Category: B

Availability

5 mg tablets

Action

Potassium-sparing diuretic with mild diuretic and antihypertensive action. Diuretic action is independent of aldosterone and carbonic anhydrase. Induces urinary excretion of sodium and reduces excretion of potassium and hydrogen ions by direct action on distal renal tubules.

Therapeutic Effect

Lowers blood pressure by excretion of sodium ion and water from the kidney while sparing potassium excretion.

Uses

Potassium-sparing effect in prevention or treatment of diuretic-induced hypokalemia in patients with CHF, hepatic cirrhosis, or hypertension. Also used in management of primary hyperaldosteronism. Usually combined with a potassium-wasting (kaliuretic) diuretic such as a thiazide or loop diuretic.

Unlabeled Uses

With hydrochlorothiazide for recurrent calcium nephrolithiasis, lithium-induced polyuria.

Contraindications

Elevated serum potassium (>5.5 mEq/L), concomitant use of other potassium-sparing diuretics; anuria, acute or chronic renal insufficiency; evidence of diabetic nephropathy; type 1 diabetes mellitus; metabolic or respiratory acidosis; pregnancy (category C); lactation. Safety in children is not established.

Cautious Use

Debilitated patients; diet-controlled or uncontrolled diabetes mellitus; cardiopulmonary disease; hepatic disease; older adult.

Route & Dosage

Diuretic
Adult: PO 5 mg/d, may increase up to 20 mg/d in 1–2 divided doses

Administration

Oral
  • Give once/d dose in the morning and schedule the second b.i.d. dose early to avoid interrupting sleep.
  • Give with food to reduce possibility of gastric distress.
  • Store at 15°–30° C (59°–86° F) in a tightly closed container unless otherwise directed.

Adverse Effects (≥1%)

Body as a Whole: Generally well tolerated. CNS: Headache, dizziness, nervousness, confusion, paresthesias, drowsiness. CV: Cardiac arrhythmias. Metabolic: Hyperkalemia, hyponatremia, positive Coombs' test. Hematologic: Aplastic anemia. Special Senses: Tinnitus; nasal congestion. Visual disturbances, increased intraocular pressure. GI: Diarrhea or constipation, anorexia, nausea, vomiting, abdominal cramps, dry mouth, thirst. Urogenital: Polyuria, dysuria, bladder spasms, urinary frequency, impotence, decreased libido. Respiratory: Dyspnea, shortness of breath. Skin: Rash, pruritus, photosensitivity reactions. Other: Weakness, fatigue, muscle cramps.

Diagnostic Test Interference

Manufacturer advises discontinuing amiloride in patients with diabetes mellitus at least 3 d before glucose tolerance test.

Interactions

Drug: Blood from blood banks, ace inhibitors (e.g., captopril), spironolactone, triamterene, potassium supplements may cause hyperkalemia with cardiac arrhythmias; possibility of increased lithium toxicity (decreased renal elimination); possibility of altered digoxin response; nsaids may attenuate antihypertensive effects. Food: potassium-containing salt substitutes or foods high in potassium increase risk of hyperkalemia.

Pharmacokinetics

Absorption: 50% from GI tract. Onset: 2 h. Peak: 6–10 h. Duration: 24 h. Elimination: 20–50% unchanged in urine, 40% in feces. Half-Life: 6–9 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for S&S of hyperkalemia and hyponatremia (see Appendix F). Hyperkalemia occurs in about 10% of patients receiving amiloride and serum potassium can rise suddenly and without warning. It is more common in older adults and patients with diabetes or renal disease.
  • Lab tests: Serum potassium levels, particularly when therapy is initiated, whenever dosage adjustments are made, and during any illness that may affect kidney function. Intermittent evaluations of BUN, creatinine, and ECG for patients with renal or hepatic dysfunction, diabetes mellitus, older adults, or the debilitated.

Patient & Family Education

  • Learn S&S of hyperkalemia and hyponatremia (see Appendix F) and report to physician immediately.
  • Do not take potassium supplements, salt substitutes, high intake of dietary potassium unless prescribed by physician.
  • Do not drive or engage in potentially hazardous activities until response to drug is known.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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