SPIRONOLACTONE

SPIRONOLACTONE (speer-on-oh-lak'tone) Aldactone, Novospiroton  Classifications: electrolytic and water balance agent; potassium-sparing diuretic; Therapeutic: potassium-sparing diuretic; antihypertensive Pregnancy Category: D

Availability

25 mg, 50 mg, 100 mg tablets

Action

Steroidal compound and specific pharmacologic antagonist of aldosterone. Presumably acts by competing with aldosterone for cellular receptor sites in distal renal tubule. Promotes sodium and chloride excretion without concomitant loss of potassium. Activity depends on presence of endogenous or exogenous aldosterone.

Therapeutic Effect

A diuretic agent that promotes sodium and chloride excretion without concomitant loss of potassium. Lowers systolic and diastolic pressures in hypertensive patients.

Uses

Clinical conditions associated with augmented aldosterone production, as in essential hypertension, refractory edema due to CHF, hepatic cirrhosis, nephrotic syndrome, and idiopathic edema. May be used to potentiate actions of other diuretics and antihypertensive agents or for its potassium-sparing effect. Also used for treatment of (and as presumptive test for) primary aldosteronism.

Unlabeled Uses

Hirsutism in women with polycystic ovary syndrome or idiopathic hirsutism; adjunct in treatment of myasthenia gravis and familial periodic paralysis.

Contraindications

Anuria, severe renal insufficiency; renal failure; diabetic nephropathy; progressing impairment of kidney function, hyperkalemia; pregnancy (category D).

Cautious Use

BUN of 40 mg/dL or greater, mild or moderate renal impairment; liver disease.

Route & Dosage

Edema Adult: PO 25–200 mg/d in divided doses, continued for at least 5 d (dose adjusted to optimal response; if no response, a thiazide or loop diuretic may be added) Child: PO 3.3 mg/kg/d in single or divided doses, continued for at least 5 d (dose adjusted to optimal response) Neonate: PO 1–3 mg/kg/d divided q12–24h Hypertension Adult: PO 25–100 mg/d in single or divided doses, continued for at least 2 wk (dose adjusted to optimal response) Primary Aldosteronism: Diagnosis Adult: PO Short Test: 400 mg/d for 4 d; long test: 400 mg/d for 3–4 wk Primary Aldosteronism Adult: PO 100–400 mg/d in divided doses

Administration

Oral

• Give with food to enhance absorption.
• Crush tablets and give with fluid of patient's choice if unable to swallow whole.
• Store in tight, light-resistant containers. Suspension is stable for 1 mo under refrigeration.

Adverse Effects (≥1%)

CNS: Lethargy, mental confusion, fatigue (with rapid weight loss), headache, drowsiness, ataxia. Endocrine: Gynecomastia (both sexes), inability to achieve or maintain erection, androgenic effects (hirsutism, irregular menses, deepening of voice); parathyroid changes, decreased glucose tolerance, SLE. GI: Abdominal cramps, nausea, vomiting, anorexia, diarrhea. Skin: Maculopapular or erythematous rash, urticaria. Metabolic: Fluid and electrolyte imbalance (particularly hyperkalemia and hyponatremia); elevated BUN, mild acidosis, hyperuricemia, gout. Body as a Whole: Drug fever. Hematologic: Agranulocytosis. CV: Hypertension (post-sympathectomy patient).

Diagnostic Test Interference

May produce marked increases in plasma cortisol determinations by Mattingly fluorometric method; these may persist for several days after termination of drug (spironolactone metabolite produces fluorescence). There is the possibility of false elevations in measurements of digoxin serum levels by RIA procedures.

Interactions

Drug: Combinations of spironolactone and acidifying doses of ammonium chloride may produce systemic acidosis; use these combinations with caution. Diuretic effect of spironolactone may be antagonized by aspirin and other salicylates. Digoxin should be monitored for decreased effect of cardiac glycoside. Hyperkalemia may result with potassium supplements, ace inhibitors, arbs, heparin may decrease lithium clearance resulting in increased tenacity; may alter anticoagulant response in warfarin. Food: Salt substitutes may increase risk of hyperkalemia.

Pharmacokinetics

Absorption: 73% from GI tract. Onset: Gradual. Peak: 2–3 d; maximum effect may take up to 2 wk. Duration: ≥2–3 d. Distribution: Crosses placenta, distributed into breast milk. Metabolism: In liver and kidneys to active metabolites. Elimination: 40–57% in urine, 35–40% in bile. Half-Life: 1.3–2.4 h parent compound, 18–23 h metabolites.

Nursing Implications

Assessment & Drug Effects

• Check blood pressure before initiation of therapy and at regular intervals throughout therapy.
• Lab tests: Monitor serum electrolytes (sodium and potassium) especially during early therapy; monitor digoxin level when used concurrently.
• Assess for signs of fluid and electrolyte imbalance, and signs of digoxin toxicity.
• Monitor daily I&O and check for edema. Report lack of diuretic response or development of edema; both may indicate tolerance to drug.
• Weigh patient under standard conditions before therapy begins and daily throughout therapy. Weight is a useful index of need for dosage adjustment. For patients with ascites, physician may want measurements of abdominal girth.
• Observe for and report immediately the onset of mental changes, lethargy, or stupor in patients with liver disease.
• Adverse reactions are generally reversible with discontinuation of drug. Gynecomastia appears to be related to dosage level and duration of therapy; it may persist in some after drug is stopped.

Patient & Family Education

• Be aware that the maximal diuretic effect may not occur until third day of therapy and that diuresis may continue for 2–3 d after drug is withdrawn.
• Report signs of hyponatremia or hyperkalemia (see Appendix F), most likely to occur in patients with severe cirrhosis.
• Avoid replacing fluid losses with large amounts of free water (can result in dilutional hyponatremia).
• Weigh 2–3 times each wk. Report gains/loss of ≥5 lb.
• Do not drive or engage in potentially hazardous activities until response to the drug is known.
• Avoid excessive intake of high-potassium foods and salt substitutes.

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