DrugindexOnline^{2nd edition}

Pronouncation: (uh-MILL-oh-ride HIGH-droe-KLOR-ide)
Class: Potassium-sparing diuretic

Trade Names:
Midamor
- Tablets 5 mg

Mechanism of Action

Pharmacology

Interferes with sodium reabsorption at distal tubule, resulting in increased excretion of water and sodium and decreased excretion of potassium.

Pharmacokinetics

Absorption

15% to 25% is absorbed; t _max is 3 to 4 h.

Distribution

About 23% is protein bound.

Metabolism

Not metabolized.

Elimination

T _1/2 is 6 to 9 h. About 50% is excreted unchanged in the urine; about 40% in the feces.

Onset

Within 2 h.

Peak

6 to 10 h.

Duration

24 h.

Indications and Usage

Treatment of CHF or hypertension (in combination with thiazide or loop diuretics) and diuretic-induced hypokalemia.

Unlabeled Uses

Reduction of lithium-induced polyuria; slowed reduction of pulmonary function in patients with cystic fibrosis (aerosol form).

Contraindications

Serum potassium more than 5.5 mEq/L; potassium supplementation; impaired renal function: spironolactone or triamterene therapy.

Dosage and Administration

Adult

PO 5 to 10 mg/day.

Lithium-Induced Polyuria

PO 10 to 20 mg/day.

Cystic Fibrosis

Dissolve in 0.3% saline and deliver by nebulizer.

Storage/Stability

Store in tightly closed container in cool location.

Drug Interactions

Angiotensin-converting enzyme inhibitors

May result in severely elevated serum potassium levels.

Potassium preparations

May severely increase serum potassium levels, possibly resulting in cardiac arrhythmias or cardiac arrest. Do not administer to patients taking potassium preparations.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Angina pectoris; orthostatic hypotension; arrhythmia.

CNS

Headache; dizziness; encephalopathy; paresthesia; tremors; vertigo; nervousness; mental confusion; insomnia; decreased libido; depression.

Dermatologic

Skin rash; itching; pruritus.

EENT

Visual disturbances; tinnitus; nasal congestion.

GI

Nausea; anorexia; diarrhea; vomiting; abdominal pain; gas pain; appetite changes; constipation; GI bleeding; abdominal fullness; thirst; dry mouth; heartburn; flatulence.

Genitourinary

Impotence; polyuria; dysuria; urinary frequency.

Hematologic

Aplastic anemia; neutropenia.

Hepatic

Jaundice.

Metabolic

Increased serum potassium levels.

Respiratory

Cough; dyspnea.

Miscellaneous

Musculoskeletal (eg, weakness; fatigue; muscle cramps; joint/back/chest pain; neck or shoulder ache).

Precautions

Monitor Hyperkalemia Monitor for signs of hyperkalemia (eg, fatigue, muscle weakness, cardiac irregularities).

Pregnancy

Category B .

Lactation

Undetermined.

Children

Safety and efficacy not established.

Renal Function

Use cautiously in patients with this condition.

Hepatic Function

With severe liver disease, hepatic encephalopathy (eg, tremors, confusion, coma, jaundice) may occur.

Diabetes mellitus

Hyperkalemia may occur.

ECG change

If ECG changes occur (eg, peaked T waves, abnormal S or P waves), withhold dose and notify health care provider.

Electrolyte imbalances and BUN increase

Hyperkalemia, hyponatremia, hypochloremia, and increases in BUN may occur.

Serum potassium levels

If sudden elevation in serum potassium level (more than 5.5 mEq/L) occurs, withhold dose and notify health care provider.

Patient Information

• Explain that dietary considerations are very important while taking this medication. Advise patient to avoid the following: Eating excessive amounts of potassium-rich foods (bananas, citrus fruits, raisins, nuts), using salt substitutes, taking medications high in potassium and eating foods high in sodium (tomatoes, pickled foods, canned foods, luncheon meats).
• Teach patient to monitor BP daily.
• Instruct patient to take medication as directed, even if feeling well.
• Encourage patient to avoid sudden changes in position to prevent orthostatic hypotension.
• Advise patient that drug may cause dizziness and blurred vision, and to use caution while driving or performing other tasks requiring mental alertness.
• Inform patient that this medication causes increased urine output.
• Teach patient signs and symptoms of hyperkalemia and hyponatremia.
• Caution patient to notify health care provider or dentist about taking this medication and notify health care provider of cramps or chronic fatigue and weakness, which are serious side effects.