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multi class comparison

Diuretic Classes: Loop vs Thiazide vs Potassium-Sparing — Site of Action, K+ Effect, Monitoring

Picking the wrong potassium direction kills. A client on furosemide needs potassium-rich foods; a client on spironolactone needs potassium restriction. Reversing that dietary teaching on the NCLEX — or at the bedside — triggers a fatal dysrhythmia.

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Comparison

Side-by-side3 compared
Comparevs
Dimension
Loop
Thiazide
Potassium-Sparing
Class & mechanism
  • Inhibit Na/K/2Cl in ascending loop of Henle
  • Inhibit Na/Cl in distal convoluted tubule
  • Aldosterone antagonist at collecting duct
Indications
  • Edema, HF, pulmonary edema
  • ★Works even in low GFR / renal impairment
  • First-line HTN
  • mild edema
  • Adjunct diuretic
  • hyperaldosteronism
Route & onset
  • PO or IV
  • IV fast for pulmonary edema
  • PO
  • ineffective when GFR is low
  • PO
  • slow onset (spironolactone)
Key assessment
  • Daily weight, I&O, blood pressure
  • Daily weight, I&O, blood pressure
  • Daily weight, I&O, blood pressure
Monitoring labs
  • Monitor electrolytes & renal function
  • Monitor for hypokalemia
  • Monitor electrolytes & renal function
  • Monitor for hypokalemia
  • Monitor electrolytes & renal function
  • ★Monitor for HYPERkalemia
Adverse effects
  • Hypokalemia, dehydration
  • ★↑glucose, ↑uric acid (gout), ↑calcium
  • Hyperkalemia
  • spironolactone gynecomastia
Toxicity / safety
  • ★Ototoxicity — avoid rapid IV push
  • Severe hyponatremia, volume depletion
  • Dangerous hyperkalemia then arrhythmias
Contraindications & interactions
  • Sulfa allergy caution
  • Sulfa allergy caution
  • Avoid K supplements / salt substitutes
Patient teaching
  • Take in the morning to avoid nocturia
  • Eat potassium-rich foods (bananas, oranges)
  • Take in the morning to avoid nocturia
  • Eat potassium-rich foods (bananas, oranges)
  • Take in the morning to avoid nocturia
  • Avoid high-potassium foods & salt substitutes
Class & mechanism

Loop

  • Inhibit Na/K/2Cl in ascending loop of Henle

Thiazide

  • Inhibit Na/Cl in distal convoluted tubule
Indications

Loop

  • Edema, HF, pulmonary edema
  • ★Works even in low GFR / renal impairment

Thiazide

  • First-line HTN
  • mild edema
Route & onset

Loop

  • PO or IV
  • IV fast for pulmonary edema

Thiazide

  • PO
  • ineffective when GFR is low
Key assessment

Loop

  • Daily weight, I&O, blood pressure

Thiazide

  • Daily weight, I&O, blood pressure
Monitoring labs

Loop

  • Monitor electrolytes & renal function
  • Monitor for hypokalemia

Thiazide

  • Monitor electrolytes & renal function
  • Monitor for hypokalemia
Adverse effects

Loop

  • Hypokalemia, dehydration

Thiazide

  • ★↑glucose, ↑uric acid (gout), ↑calcium
Toxicity / safety

Loop

  • ★Ototoxicity — avoid rapid IV push

Thiazide

  • Severe hyponatremia, volume depletion
Contraindications & interactions

Loop

  • Sulfa allergy caution

Thiazide

  • Sulfa allergy caution
Patient teaching

Loop

  • Take in the morning to avoid nocturia
  • Eat potassium-rich foods (bananas, oranges)

Thiazide

  • Take in the morning to avoid nocturia
  • Eat potassium-rich foods (bananas, oranges)

★ marks the fact that sets a column apart.

Clinical Pearl

Loop and thiazide lose K+ — teach "eat bananas"; spironolactone keeps K+ — teach "avoid bananas."

Component Topics

Potassium-Sparing DiureticsThiazide DiureticsLoop Diuretics

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