Furosemide, bumetanide, torsemide, and ethacrynic acid are "high-ceiling" loop diuretics acting primarily at the ascending limb of the loop of Henle.

The effectiveness of these agents is related to their site of action because reabsorption of about 30 - 40% of the filtered sodium and chloride load occurs at the ascending loop. Distal sites are not able to compensate completely for this magnitude of reduction of NaCl reabsorption.

Loop diuretics increase urinary Ca²⁺ in contrast to the action of thiazides.

Loop diuretics also increase renal blood flow by decreasing renal vascular resistance.

These drugs are beneficial in managing systemic and pulmonary fluid overload produced by congestive heart failure (CHF). By i.v. administration they are particularly effective in resolving acute pulmonary edema.

Adverse Effects

• Ototoxicity

• Furosemide and ethacrynic acid block renal excretion of uric acid by competition with renal secretory and biliary secretory systems.

  • Therefore these agents can precipitate gout.

• Potassium depletion.