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Spironolactone (Aldactone, CaroSpir)

Potassium-sparing diuretic / aldosterone antagonist

Mechanism of action

Competitively blocks the aldosterone receptor in the distal nephron, reducing sodium and water retention while sparing potassium. Used for resistant hypertension, heart failure (mortality benefit in HFrEF), cirrhotic ascites, and hyperaldosteronism. Also used for acne and hirsutism in women due to anti-androgen activity.

Adverse effects

Life-threatening / NCLEX-tested

  • Hyperkalemia — life-threatening; the central monitoring concern
  • Severe hypotension when stacked with ACE/ARB and diuretics
  • Acute kidney injury, especially in volume depletion
  • Gynecomastia and breast tenderness (anti-androgen effect)
  • Menstrual irregularities and decreased libido

Side effects

Common — what to teach

  • Mild GI upset, nausea
  • Headache
  • Drowsiness
  • Dizziness on standing
  • Voice deepening (rare)

Food & drug interactions

ACE inhibitors, ARBs, potassium supplements, salt substitutes (KCl-based), and high-K+ foods all compound hyperkalemia risk. NSAIDs blunt the antihypertensive effect and worsen renal function. Lithium levels rise. Always reconcile potassium intake — teach patients NOT to use "Lite Salt" or No Salt substitutes.

Nursing implications

Assessment, monitoring, patient teaching

  • Monitor serum K+ and creatinine at baseline, 1–2 weeks after start or dose change, and periodically
  • Counsel against potassium-rich salt substitutes and avoid routine potassium supplementation
  • Teach signs of hyperkalemia: muscle weakness, paresthesias, palpitations, nausea
  • For heart failure use, reinforce that the goal is mortality reduction — adherence matters even if symptoms are stable
  • Take in the morning with food
  • Discuss gynecomastia with male patients up front so it doesn't surprise them at month 2

When to hold / contraindications

  • Serum K+ > 5.0 mEq/L
  • Acute kidney injury or significant rise in creatinine
  • Severe hyponatremia (Na+ < 130) until corrected
  • Anuria
  • Pregnancy (use only if benefit clearly outweighs risk)

Memory anchor

"Spirono-spares-K+" — the only common diuretic that raises potassium. The HF mortality benefit (RALES trial) is why nurses tolerate the gynecomastia.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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