Loop Diuretics

Loop diuretics can result in significant diuresis, which is the reason these drugs are used frequently in the treatment of acute heart failure exacerbations and pulmonary edema.  Loop diuretics are also used chronically to manage fluid volumes. Loop diuretics are potassium and calcium wasting, so also are used to treat hyperkalemia and hypercalcemia.  Loop diuretics function by inhibiting the Sodium-Potassium-Chloride co-transporter in the ascending loop of Henle, which results in retention of sodium and potassium retention in the renal tubule.  Downstream there is not enough sodium resorption to make up for the loss in the ascending loop of Henle. Loop diuretics commonly result in hypokalemia.  Hyperuricemia occurs, which can precipitate gout attacks. Additionally, loop diuretics can be ototoxic, so special care must be taken to avoid use with other ototoxic drugs.

Class Drugs

• Bumetanide

• Ethacrynic Acid

• Furosemide

• Torsemide

Class Mechanism of Action

Inhibition of Sodium/Potassium/2Chloride (Na/K/2Cl) co-transport in the luminal membrane of the ascending limb of the loop of Henle

• Decreases reabsorption of Na/K/Cl

• Ascending loop of Henle accounts for most reabsorption of NaCl, and downstream reabsorption cannot recoup losses

Renal Tubule - Primary sites of action of diuretics.

Class Applications

Hypertension

• Initially, reduces blood volume, resulting in decreased cardiac output and lower blood pressure

• Later, most effects are from decreased peripheral vascular resistance

Heart Failure/ Pulmonary Edema

• Decreases blood volume

Hypercalcemia

• Used in conjunction with fluids to reduce calcium levels

• Loop diuretics increase excretion of calcium into the urine

Hyperkalemia

• Reduces serum potassium by increasing urinary excretion of potassium

Class Adverse Effects

Ototoxicity

• Permanent or temporary

• Increased risk with other ototoxic drugs (such as aminoglycosides)

Hyperuricemia

• Furosemide and ethacrynic acid inhibit uric acid secretion

• Can precipitate gout attacks

Volume depletion

Hypokalemia

Hypomagnesemia

Allergy

• Possible cross-reactivity with other sulfa based compounds

Drug Table

Drug Name	Application	Comments	Image
Bumetanide			"Bum" "Tide"
Ethacrynic Acid		Does not have sulfa component	"Ethan" "Crying""
Furosemide			"Fur" "Semi"
Torsemide			"Torn Semi"