Loop Diuretics

Summary

Loop diuretics include the drug names furosemide, bumetanide, torsemide, and ethacrynic acid. 

They work by blocking the sodium-potassium-chloride transporter in the kidney. This leads to decreased reabsorption of sodium, potassium, and chloride, which are then lost in the urine. Most loop diuretics are sulfa drugs, and should not be used in patients with a sulfa allergy. Loop diuretics are among the most powerful diuretics available. 

Clinically, loop diuretics are used to treat edema, including pulmonary edema. They are also used to treat hypertension and heart failure.

Side effects of loop diuretics include hypotension, hyperglycemia, hyperuricemia, and dehydration. Ototoxicity is another potential side effect, and can occur if the loop diuretic is administered too quickly. Loop diuretics can cause electrolyte imbalances such as hypokalemia, hyponatremia, hypocalcemia, hypochloremia, and hypomagnesemia.

Patients on loop diuretics should take their weight daily to monitor their fluid status, and take the diuretic in the morning.

Key Points

• Loop Diuretics
  • Drug Names
    • Furosemide (Lasix)
    • Bumetanide (Bumex)
    • Torsemide (Demadex)
    • Ethacrynic Acid (Edecrin)
  • Mechanism
    • Block the NaK2Cl transporter
      • Blocks the reuptake of sodium, potassium, and chloride in the loop of henle, meaning more of these ions are excreted in the urine
      • Fluid follows ions, so as a result less fluid is reabsorbed back into the body → more urine
    • Powerful diuretic effect
      • Of all the types of diuretics, loop diuretics are the strongest and work the most quickly
    • Sulfa Drug
      • Cross sensitivity in patients with a sulfa allergy
      • If patients are allergic to other sulfa drugs (i.e. sulfonamide antibiotics) it is not recommended that they use loop diuretics
      • **Note: ethacrynic acid is not a sulfa drug, so it is given to patients who have a sulfa allergy who need to be on a loop diuretic
    • Works even with renal impairment
      • Loop diuretics are unique because even with renal impairment (i.e. low creatinine clearance, kidney failure) they still have their intended effect
  • Clinical Use
    • Edema
      • Fluid buildup in the body, that commonly presents in the lower extremities
    • Heart Failure
      • By removing fluid, loop diuretics decrease blood volume and reduce the workload of the heart
    • Pulmonary Edema
      • Fluid accumulation in the lungs
    • Hypertension
      • By removing fluid, loop diuretics decrease blood volume, thus effectively decreasing blood pressure
  • Side Effects
    • Electrolyte Imbalances (everything low!)
      • Hypokalemia
        • Loop diuretics block the reabsorption of potassium (often called “potassium wasting”)
        • Encourage patients to eat a high potassium diet
        • May also be prescribed a potassium supplement
        • Use digoxin with caution - hypokalemia can cause digoxin toxicity
      • Hyponatremia
      • Hypocalcemia
      • Hypochloremia
      • Hypomagnesemia
    • Dehydration
      • Encourage adequate fluid intake to prevent dehydration
    • Hypotension
    • Ototoxicity
      • Can manifest as hearing loss or tinnitus (ringing in the ears)
      • When giving IV, make sure the drug is injected or infused slowly. Too fast of an injection can cause ototoxicity.
      • Use with caution with other ototoxic drugs (i.e. aminoglycoside antibiotics)
    • Hyperglycemia
      • Monitor blood glucose, especially in diabetic patients
    • Hyperuricemia
      • Loop diuretics increase blood uric acid levels, putting patient at increased risk of developing gout
  • Nursing Considerations
    • Take daily weights
      • One of the best way to monitor fluid retention/loss in the body is by weighing the patient daily
      • For best results, weigh around the same time each day with the same amount of clothing
      • Weight gain should be reported, as it is an indication that the patient may not be losing fluid like they’re supposed to
    • Administer early in the day
      • Administering too close to bedtime can cause nocturia, disrupting the patient’s sleep patterns and increasing their risk for falls