Spironolactone

Pronunciation: SPEER-oh-no-LAK-tone
Class: Potassium-sparing diuretic

Trade Names

Aldactone
- Tablets 25 mg
- Tablets 50 mg
- Tablets 100 mg

Spironolactone
- Tablets 25 mg

Pharmacology

Competitively inhibits aldosterone in distal tubules, resulting in increased excretion of sodium and water and decreased excretion of potassium.

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Pharmacokinetics

Absorption

Spironolactone is rapidly and extensively metabolized. Food increases bioavailability by almost 100%.

Distribution

Spironolactone is greater than 90% bound to plasma proteins.

Metabolism

Sulfur-containing products are predominant metabolites and are thought to be primarily responsible together with spironolactone for the therapeutic effect of the drug.

Elimination

Metabolites are excreted primarily in the urine and secondarily in bile.

Indications and Usage

Short-term preoperative treatment of primary hyperaldosteronism; long-term maintenance therapy for idiopathic hyperaldosteronism; management of edematous conditions in CHF, cirrhosis of liver and nephrotic syndrome; management of essential hypertension; treatment of hypokalemia.

Unlabeled Uses

Treatment of hirsutism; relief of PMS symptoms; short-term treatment of familial male precocious puberty; and short-term treatment of acne vulgaris.

Contraindications

Anuria; acute renal insufficiency; impaired renal excretory function; hyperkalemia.

Dosage and Administration

PO 400 mg/day for 4 days (short test) or 3 to 4 wk (long test).

PO 100 to 400 mg daily in single or divided doses.

PO 25 to 200 mg/day in single or divided doses.

PO 3.3 mg/kg/day in single or divided doses.

PO 50 to 100 mg/day in single or divided doses.

PO 1 to 2 mg/kg twice daily.

PO 25 to 100 mg/day when oral potassium or other potassium-sparing regimens are inappropriate.

Storage/Stability

Suspension is stable for 30 days under refrigeration. Protect from light. Store tablets at room temperature.

Drug Interactions

May result in severely elevated serum potassium levels.

May decrease digoxin clearance, resulting in increased serum digoxin levels and toxicity; may attenuate inotropic action of digoxin.

May decrease therapeutic response to mitotane.

May severely increase serum potassium levels, possibly resulting in cardiac arrhythmias or cardiac arrest. Do not take with potassium preparations.

May result in decreased diuretic effect.

Laboratory Test Interactions

Drug may cause falsely elevated serum digoxin values with radioimmunoassay (assay specific) for measuring digoxin.

Adverse Reactions

CNS

Drowsiness; lethargy; headache; mental confusion; ataxia.

Dermatologic

Maculopapular or erythematous cutaneous eruptions; urticaria.

GI

Cramping; diarrhea; gastric bleeding; gastric ulceration; gastritis; vomiting.

Genitourinary

Inability to achieve or maintain erection.

Hematologic

Agranulocytosis.

Hepatic

Hyperchloremic metabolic acidosis in decompensated hepatic cirrhosis.

Miscellaneous

Gynecomastia; irregular menses or amenorrhea; postmenopausal bleeding; hirsutism; deepening of voice; drug fever; carcinoma of breast.

Precautions

Pregnancy

Category D .

Lactation

Excreted in breast milk.

Electrolyte imbalances and BUN increase

Hyperkalemia (serum potassium greater than 5.5 mEq/L), hyponatremia, hypochloremia and increases in BUN may occur.

Overdosage

Symptoms

Electrolyte imbalance.

Patient Information

• Explain that medication's full diuretic effect may not be achieved for 1 to 2 wk.
• Instruct patient to avoid large quantities of potassium-rich foods or potassium salt substitutes.
• For patient being treated for hypertension, explain that patient may feel tired for several weeks because body needs to adjust to lowered BP.
• Instruct patient to take drug with food to minimize GI irritation.
• Tell patient to weigh self twice weekly and to notify health care provider of any increase.
• Instruct patient to notify health care provider if new symptoms develop.
• Tell patient to report these symptoms to health care provider: GI cramping, diarrhea, lethargy, thirst, headache, skin rash, menstrual abnormalities, deepening of voice, and breast enlargement in men.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.

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