Question

2 part question:

Loop diuretics, such as furosemide, are NOT potassium sparing diuretics

1. What does this mean? Explain the molecular events that determine the mechanism by which furosemide does not spare potassium.

2. Why should furosemide and digoxin not be administered concurrently?

Answer 1

1. ANS: Potassium-sparing diuretics can cause hyperkalemia and the loop diuretics, such as furosemide can cause low serum potassium concentration (hypokalemia), so the given above statement can stated as “Loop diuretics, such as furosemide, are NOT potassium sparing diuretics”.

Potassium sparing drugs act as antagonists of aldosterone on the kidney. These drugs increase diuresis or increased urination by interfering with sodium- potassium exchange in the kidneys. These drugs do not have any effect on the potassium ion concentration in the blood. These drugs when used at a low dose have showed no reduction in blood pressure levels. As the sodium and potassium exchange is hindered by this drug, it prevents sodium reabsorption and potassium and hydrogen ion secretion. So there is chance of acidosis happening in the patients treated with this drug.

Furosemide mechanism of action:
Furosemide is one kind of loop diuretics, it can mostly affect on the kidneys loop of Henle ascending limb. Furosemide modulates the fluid and electrolyte balance of the individual and It can acts at the luminal side of the thick ascending limb of the loop of Henle and blocks the NKCC2 (sodium-potassium-chloride cotransporter). This, in turn, inhibits the reabsorption of chloride and prevents the transportation of the sodium ions from the lumen of the loop of Henle into the basolateral interstitium. As a result, the ability of nephron for water reabsorption is decreased and the output of urine is increased.

2. ANS: Interaction between digoxin and furosemide is one of the most common drug–drug interactions like increased frequency of cardiac arrhythmias and electrolyte abnormalities are generally taken in between both drugs, so the combined use of digoxin and diuretics should be avoided if possible.