Furosemide

• Furosemide (Lasix), bumetanide (Bumex), and ethacrynic acid (Edecrin) 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 rarely used in the management of hypertension because of their short duration of action and the availability of better drugs.

• Adverse Effects

  • Ototoxicity

  • Furosemide (Lasix) and ethacrynic acid (Edecrin) block renal excretion of uric acid by competition with renal secretory and biliary secretory systems.Therefore these agents can precipitate gout.

  • Potassium depletion.

Category: Pharmacology Notes