USMLE

Loop Diuretics

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Cardiovascular Drugs
  1. Beta Blockers
  2. ACE Inhibitors
  3. Angiotensin II Receptor Blockers (ARBs)
  4. Adenosine
  5. Atropine
  6. Amiodarone
  7. DHP Calcium Channel Blockers
  8. Non-DHP Calcium Channel Blockers
  9. Clonidine
  10. Clopidogrel
  11. Digoxin
  12. Dopamine
  13. Epinephrine
  14. Hydralazine
  15. Loop Diuretics
  16. Nitroglycerin
  17. Norepinephrine
  18. Spironolactone
  19. Statins
  20. Thiazide Diuretics

Summary

Loop diuretics are a class of medications that cause diuresis, or fluid loss, by increasing urine output. They work by acting at the loop of Henle in the kidney in order to block sodium and other ions from being reabsorbed, which eventually leads to reduced water reabsorption and fluid loss in the urine. The most common loop diuretic drugs are furosemide, torsemide, and bumetanide. Loop diuretics are the most powerful diuretic drugs and are used in the clinical setting to treat fluid overload states, like pulmonary edema caused by heart failure, peripheral edema, and ascites due to cirrhosis. Potential side effects include ototoxicity and hypokalemia.

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