Loop Diuretics - A Brief Summary

Introduction: A diuretic is a medicine that causes an increase in urine and the amount of water excreted from the kidneys. Loop diuretics are the drugs that act on the the ascending loop of Henle in the kidney to cause diuresis and are so named as loop diuretics.

Mode of Action: Loop diuretics inhibit the Na+/K+/2Cl- co-transporter in the thick ascending loop of Henle, in the kidneys and stop the transport of sodium chloride out of the tubule into the interstitial tissue, causing a decrease in sodium and chloride re-absorption. They act on the chloride-binding site and have a direct inhibiting effect on the carrier.
Inhibition of this transporter leads to a significant increase in concentration of ions in the tubule and reduced hypertonicity in the surrounding interstitium, causing less water to be reabsorbed into the blood. This causes more urine to be produced and a decrease in blood volume.

Clinical Uses: Loop diuretics are basically used for following conditions;

• Edema associated with heart failure
• Fluid accumulation in renal impairment or nephrotic syndrome.
• Edema with Hepatic cirrhosis
• Hypertension
• Sometimes as an adjuvant in cerebral or pulmonary edema where rapid diuresis is required.

Examples of Loop Diuretics: Common drugs in the group of loop diuretics include:

• Bumetanide
• Ethacrynic acid
• Furosemide (Lasix)
• Torsemide

Adverse Effects: A few of the side effects related to loop diuretics include:

• Dose related diuresis and electrolyte imbalances
• Hyponatremia
• Hypokalemia
• Dehydration
• Hypomagnesemia
• Hyperuricemia
• Gout
• Dizziness
• Postural hypotension
• Ototoxicity is rare but a serious side effect
• Renal failure if taken along with NSAIDS and ACE inhibitors
• Sometimes an abnormal heart rhythm due to electrolyte imbalance.