What is the ranking of diuretics by strength and their corresponding dosing?

Diuretics Ranked by Strength with Appropriate Dosing

Loop diuretics are the most potent class of diuretics, followed by thiazide diuretics, and then potassium-sparing diuretics, with specific dosing recommendations for each agent. 1

Loop Diuretics (Strongest)

Loop diuretics produce the most intense and shortest diuresis, making them the most potent class of diuretics available 1.

• Furosemide:

  • Initial dose: 20-40 mg once or twice daily
  • Usual daily dose: 40-240 mg
  • Duration of action: 6-8 hours 1
  • May require doses up to 600 mg/day in severe edematous states 2

• Bumetanide:

  • Initial dose: 0.5-1.0 mg once or twice daily
  • Usual daily dose: 1-5 mg
  • Duration of action: 4-6 hours 1
  • Approximately 40 times more potent than furosemide on a mg-per-mg basis 3

• Torsemide:

  • Initial dose: 5-10 mg once daily
  • Usual daily dose: 10-20 mg
  • Duration of action: 12-16 hours 1
  • Better oral bioavailability than furosemide 3

Thiazide and Thiazide-like Diuretics (Intermediate)

Thiazides produce a more moderate but longer-lasting diuresis than loop diuretics 1.

• Hydrochlorothiazide:

  • Initial dose: 25 mg once daily
  • Usual daily dose: 12.5-100 mg
  • Duration of action: 6-12 hours 1
  • Lower doses (12.5 mg) may be appropriate for elderly patients or in combination therapy 4

• Chlorthalidone:

  • Initial dose: 12.5-25 mg once daily
  • Usual daily dose: up to 100 mg
  • Duration of action: 24-72 hours 1
  • More potent than hydrochlorothiazide at comparable doses 3

• Metolazone:

  • Initial dose: 2.5 mg once daily
  • Usual daily dose: 2.5-10 mg
  • Duration of action: 12-24 hours 1
  • Often used in combination with loop diuretics for resistant edema 1

• Indapamide:

  • Initial dose: 2.5 mg once daily
  • Usual daily dose: 2.5-5 mg
  • Duration of action: 36 hours 1

Potassium-Sparing Diuretics (Weakest)

These agents have the weakest diuretic effect but help conserve potassium 1.

• Spironolactone (Aldosterone antagonist):

  • Initial dose: 12.5-25 mg once daily
  • Usual daily dose: up to 50 mg
  • For heart failure: Start with 25 mg daily, may increase to 50 mg daily if tolerated 5
  • For resistant edema: May require up to 100-200 mg daily 1

• Eplerenone (Aldosterone antagonist):

  • Initial dose: 25 mg once daily
  • Usual daily dose: up to 50 mg 1
  • More selective than spironolactone with fewer endocrine side effects 6

• Amiloride:

  • Initial dose: 2.5 mg once daily
  • Usual daily dose: up to 5 mg 1

• Triamterene:

  • Initial dose: 25 mg once daily
  • Usual daily dose: up to 50 mg 1

Clinical Applications and Considerations

Combination Therapy

• Loop diuretics and thiazides act synergistically and can be combined to treat resistant edema, though this increases the risk of adverse effects 1
• When combining diuretics, start with low doses and monitor closely for electrolyte disturbances and volume depletion 1
• Metolazone specifically is often added to loop diuretics for enhanced effect in severe heart failure 1

Diuretic Resistance

• Can be addressed by:
  • Increasing the dose of the loop diuretic
  • Switching to continuous infusion (for inpatients)
  • Adding a thiazide diuretic to a loop diuretic 7
  • Switching to a loop diuretic with better bioavailability (e.g., torsemide instead of furosemide) 3

Important Cautions

• Do not use thiazides if estimated glomerular filtration rate < 30 mL/min/1.73 m², except when prescribed synergistically with loop diuretics 1
• Potassium-sparing diuretics should not be combined with each other, particularly MRAs (spironolactone/eplerenone) should not be combined with amiloride or triamterene due to hyperkalemia risk 1
• Monitor electrolytes, renal function, and blood pressure within 1-4 weeks of initiation or dose change 4
• Adverse effects increase with higher doses and longer duration of action 8

Relative Potency

• 40 mg of furosemide ≈ 1 mg of bumetanide ≈ 10-20 mg of torsemide (loop diuretics) 3
• 25 mg of chlorthalidone > 50 mg of hydrochlorothiazide in blood pressure reduction 3

The aim of diuretic therapy is to achieve and maintain euvolemia with the lowest achievable dose, adjusting according to individual needs over time 1.