Medicine & USMLE

Loop Diuretics

Cardio Drugs - Diuretics
  1. Loop Diuretics
  2. Thiazide Diuretics
  3. Spironolactone
  4. Mannitol


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Key Points

  • Key Drugs
    • Furosemide
    • Bumetanide
    • Torsemide
    • Ethacrynic acid
    • Mechanism (Saunders, Wolters Kluwer)
      • Causes diuresis by inhibiting sodium-potassium-chloride triple transporter at the ascending loop of Henle (hence the name… Loop Diuretics)
      • Loop diuretics are the most powerful diuretics and are rapid-acting. Onset of drug IV is 5 minutes
      • Work even in cases of severe renal impairment (unlike thiazides and potassium-sparing diuretics)
    • Clinical Use (Saunders, Mictlan)
      • Remove Excess Fluid (Diuresis)
        • Pulmonary edema caused by Heart Failure
        • Peripheral edema
        • Hypertension
        • Ascites associated with liver failure (cirrhosis)
        • Nephrotic syndrome
        • Will lead to increased urination
          • Avoid administering late in the day to prevent nocturia and risk of falling. Provide easy access to the bathroom if a catheter is not present.
          • Report urine output less than 30 mL/hour
    • Side Effects and Adverse Reactions (Saunders)
      • Electrolyte imbalances
        • Hypokalemia (potassium-wasting)
          • Can lead to muscle cramps, weakness, and life-threatening heart arrhythmias
          • Closely monitor potassium levels
          • Supplement with potassium, educate patient to eat foods high in potassium, do not administer if patient has low potassium (below 3.5)
        • Hyponatremia
        • Hypocalcemia
        • Hypomagnesemia
      • Ototoxicity
        • Furosemide only
        • Caused by too rapid of administration
          • Do not give faster than 4 mg/min IV
      • Dehydration
        • Daily weights are the best indicator of fluid retention/fluid loss.
          • Encourage patients on furosemide, especially those with heart failure, to measure weight daily and contact their doctor with extreme weight gain or weight loss.
        • Closely monitor intake and output in the hospital setting.
        • Patients should monitor how much liquid they intake and follow provider’s instruction
          • Too much fluid intake counters the effect of the diuretic, too little liquid can cause dehydration
      • Hypotension
        • Due to sudden drop in fluid volume
        • Closely monitor blood pressure
        • Encourage patient to change positions slowly to minimize dizziness associated with orthostatic hypotension
      • Hyperuricemia
        • Use with caution in patients experiencing gout