ALDACTONE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ALDACTONE (ALDACTONE).
Competitive aldosterone receptor antagonist; increases sodium and water excretion, decreases potassium excretion at distal convoluted tubule.
| Metabolism | Extensively hepatic via deacetylation to active metabolite canrenone; CYP3A4 involvement. |
| Excretion | Renal: 50-60% as metabolites (canrenone, other sulfur-containing metabolites), minor as unchanged drug; Biliary/Fecal: ~30-40% |
| Half-life | Spironolactone: 1.4-2.0 hours; Active metabolites (canrenone): 16.5-21.5 hours, clinically relevant for dosing interval |
| Protein binding | Spironolactone: >90%, primarily to albumin; Canrenone: >90% |
| Volume of Distribution | Vd/F: 130-150 L (spironolactone), indicating extensive tissue distribution; weight-based equivalent ~2 L/kg |
| Bioavailability | Oral: ~60-80% (spironolactone), food increases absorption |
| Onset of Action | Oral: diuresis within 2-3 hours; antihypertensive effect within 3-7 days |
| Duration of Action | Diuretic effect persists 2-3 days after discontinuation; antihypertensive effect may last 5-7 days due to active metabolites |
| Action Class | Potassium- sparing Diuretics |
| Brand Substitutes | Aldobloc 25mg Tablet, Spirix 25mg Tablet, Spiromax 25mg Tablet, Spirolact 25mg Tablet, Spironot 25 Tablet |
Initial: 50-100 mg orally once daily; may increase to 100-400 mg/day in divided doses (once to twice daily).
| Dosage form | TABLET |
| Renal impairment | eGFR 30-60 mL/min: caution; eGFR <30 mL/min: use not recommended due to risk of hyperkalemia. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated. |
| Pediatric use | Initial: 1-3 mg/kg/day orally in divided doses (once or twice daily); maximum 12 mg/kg/day. |
| Geriatric use | Start at lowest dose (25 mg once daily); monitor electrolytes and renal function closely due to age-related decline in renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ALDACTONE (ALDACTONE).
| Breastfeeding | Spironolactone and its metabolite canrenone are excreted into human breast milk. The M/P ratio is not well established, but estimated relative infant dose is low (<1% of maternal weight-adjusted dose). However, due to potential antiandrogenic effects in the nursing infant, caution is advised. Use only if clearly needed and monitor infant for adverse effects. |
| Teratogenic Risk | Aldactone (spironolactone) is contraindicated in pregnancy due to antiandrogenic effects. In animal studies, feminization of male fetuses occurred. Human data are limited but suggest potential risk of ambiguous genitalia in male fetuses exposed during the first trimester. Use is not recommended in pregnant women; alternative diuretics are preferred. |
■ FDA Black Box Warning
Spironolactone has been shown to be a tumorigen in chronic toxicity studies in rats. Use only when other therapies are inadequate.
| Serious Effects |
Anuria, acute renal insufficiency, significant renal impairment (eGFR <30 mL/min), hyperkalemia, Addison's disease, concomitant use with eplerenone or other potassium-sparing diuretics.
| Precautions | Hyperkalemia risk (especially with renal impairment, ACE inhibitors, ARBs, NSAIDs); monitor potassium levels. Can cause gynecomastia, menstrual irregularities. Avoid concomitant use with potassium supplements. Use caution with hepatic impairment. |
| Food/Dietary | Avoid high-potassium foods (e.g., bananas, oranges, tomatoes, spinach, potatoes, avocados, dried fruits) and potassium-containing salt substitutes to reduce risk of hyperkalemia. Grapefruit juice may increase spironolactone levels; limit or avoid consumption. Alcohol may enhance hypotensive effects. |
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| Fetal Monitoring | In pregnant women inadvertently exposed, monitor fetal growth and anatomy via ultrasound. For lactating women, monitor infant for signs of electrolyte imbalance, growth, and development. Monitor maternal blood pressure, serum electrolytes (especially potassium), and renal function regularly. |
| Fertility Effects | Spironolactone may impair fertility in women by causing menstrual irregularities and anovulation due to its antiandrogenic and progesterone-like effects. Reversible upon discontinuation. In men, it may cause gynecomastia and erectile dysfunction; effect on spermatogenesis is unclear. |
| Clinical Pearls | Monitor serum potassium and renal function closely; avoid use with other potassium-sparing diuretics or potassium supplements unless hypokalemia confirmed. Aldactone (spironolactone) can cause gynecomastia and menstrual irregularities due to antiandrogen effects. Onset of diuresis is slow (2-3 days); maximal effect may take 2 weeks. Use with caution in patients with hepatic impairment due to risk of hyperkalemia. |
| Patient Advice | Take with food to reduce gastrointestinal upset. · Avoid salt substitutes containing potassium. · Report symptoms of hyperkalemia: muscle weakness, fatigue, palpitations, paresthesias. · May cause dizziness or drowsiness; avoid driving until response is known. · Do not stop abruptly without consulting healthcare provider. · Monitor blood pressure regularly as directed. · Inform all healthcare providers you are taking spironolactone. · May cause breast enlargement or tenderness in men; discuss if bothersome. |