Loop Diuretics (FETT)

Diuretics

FUROSEMIDE (sulfonamides)

• Blockage of Na+-K+-2Cl-cotransporter in the thick ascending loop of Henle

  • Diminishing concentration gradient between the (usually hypertonic) renal medulla and the cortex → concentration of urine is no longer possible → increased diuresis

  • Decreased reabsorption of Ca2+ and Mg2+

• Increased PGE release (can be inhibited by NSAIDs)

  • Dilation of renal afferent arterioles → diuresis

  • General venodilation (rapid venous pooling) → ↓ cardiac preload

• Metabolic imbalances

  • Hypokalemia, hypomagnesemia, hypocalcemia, hypochloremia, hyponatremia (moderate)

  • Metabolic alkalosis

  • Hyperuricemia/gout

  • Hyperglycemia

• Ototoxicity (potentially permanent hearing damage): especially high risk with ethacrynic acid

• Dehydration/hypovolemia

• Sulfonamide hypersensitivity (except ethacrynic acid, which can be used for diuresis in patients with allergies to sulfonamides) → rash, interstitial nephritis

To recall the side effects of loop diuretics, think of “GO PANDA”: Gout, Ototoxicity, low Potassium, Allergy, Nephritis, Dehydration, Alkalosis.

To remember that loop diuretics are ototoxic, imagine a vertical loop of a roller coaster and deafening screams of people passing through it.

Hypokalemia and/or hypomagnesemia can lead to life-threatening arrhythmias!

• Hypertension

• Edema

  • Cardiac (acute and congestive heart failure, peripheral edema, lung edema)

  • Renal (nephrotic syndrome)

  • Hepatic (liver cirrhosis)

• Renal failure (acute and chronic)

• Hypercalcemia

• Forced diuresis

  • Definition: massive diuresis for forced renal elimination of (toxic) substances

  • Implementation: IV administration of large amounts of fluids in combination with loop diuretics

  • Indications: hypercalcemic crisis, severe hyperkalemia, rhabdomyolysis, intoxication (e.g., lithium)

• Sequential nephron blockade

  • Used to overcome resistance to diuretic treatment

  • Method: combination of loop diuretics and thiazides → restoration of diuretic effects

Because of the increased risk of hypokalemia and hypovolemia during forced diuresis, rigorous monitoring is necessary.