Loop diuretics

Loop diuretics

Loop (high ceiling) diuretics are highly potent drugs. They include bumetanide, ethacrynic acid, and furosemide.

Pharmacokinetics

Loop diuretics are absorbed well in the GI tract and are rapidly distributed. These diuretics are highly protein bound. They undergo partial or complete metabolism in the liver, except for furosemide, which is excreted primarily unchanged. Loop diuretics are excreted primarily by the kidneys.

Pharmacodynamics

Loop diuretics are the most potent diuretics available, producing the greatest volume of diuresis (urine production). Bumetanide’which is 40 times more potent than furosemide’is the shortest-acting diuretic. Loop diuretics also have a high potential for causing severe adverse reactions.

 

Warning!

Loop diuretics warning

Loop diuretics, with the exception of ethacrynic acid, contain sulfa. A patient who has an allergy to sulfa may experience an allergic reaction to loop diuretics. Use with caution, and alert the patient to this possibility.

The scoop on the loop

Loop diuretics received their name because they act primarily on the thick, ascending loop of Henle (the part of the nephron responsible for concentrating urine) to increase the secretion of sodium, chloride, and water. These drugs also inhibit sodium, chloride, and water reabsorption in the proximal tubule.

Pharmacotherapeutics

Loop diuretics are used to treat edema associated with renal disease, hepatic cirrhosis, and heart failure, as well as to treat hypertension (usually with a potassium-sparing diuretic or potassium supplement to prevent hypokalemia).

Ethacrynic acid may also be used for the short-term management of ascites due to malignancy, idiopathic edema, or lymphedema. Furosemide may be used with mannitol to treat cerebral edema.

Drug interactions

Loop diuretics produce a variety of drug interactions:

• The risk of ototoxicity (damage to the organs of hearing) increases when aminoglycosides and cisplatin are taken with loop diuretics (especially with high doses of furosemide). 
• Loop diuretics reduce the hypoglycemic effects of oral antidiabetic drugs, possibly resulting in hyperglycemia.
• These drugs may increase the risk of lithium toxicity.
• The risk of electrolyte imbalances that can trigger arrhythmias increases when cardiac glycosides and loop diuretics are taken together.
  
  
• Use with digoxin may cause additive toxicity, increasing the risk of digoxin toxicity and arrhythmias.

Warning!

Adverse reactions to loop diuretics

The most common adverse reactions to loop diuretics include:

• fluid and electrolyte imbalances (including metabolic alkalosis, hypovolemia, hypochloremia, hypochloremic alkalosis, hyperglycemia, hyperuricemia, dehydration, hyponatremia, hypokalemia, and hypomagnesemia)
• transient deafness
• tinnitus
• diarrhea
• nausea
• vomiting
• abdominal pain
• impaired glucose tolerance
• dermatitis
• paresthesia
• hepatic dysfunction
• photosensitivity
• orthostatic hypotension