Loop Diuretics (Furosemide)

Question 1

What are the common indications of a loop diuretic such as furosemide.?

Answer 1

1) SOB in acute pulmonary oedema.
2) fluid overload in chronic heart failure.
3) fluid overload in liver failure (ascites), renal disease.

Question 2

What is the mechanism of action of furosemide ( a loop diuretic)?

Answer 2

Furosemide (loop diuretic) works on the ASCENDING LOOP OF HENLE by inhibiting the Na+/K+/2Cl- co transporter. Normally this transporter allows ions to move out of the lumen and into the epithelial cells. Water follows via osmosis. However furosemide stops this from happening so water remains in the lumen. Leading to increased urine output.

2) Causes dilatation of capacitance veins => reduces preload => increases contractibility of overstretched heart muscles.

Question 3

What are the adverse effects of furosemide (loop diuretic)?

Answer 3

1) Dehydration
2) Hypotension
3) Low electrolyte state
4) hearing loss + tinnitus

Question 4

What conditions can worsen with furosemide?

Answer 4

1) Hepatic encephalopathy can worsen dur to hypokalaemia / hyponatraemia.
2) Gout can worsen due to decreased uric acid secretion.

Question 5

What are the main interactions of furosemide?

Answer 5

Furosemide interacts with drugs excreted by the kidney. Leading to

1) increased Lithium
2) digoxin toxicity
3) aminoglycosides (otoxicity and nephrotoxicity)

Question 6

What routes can furosemide be administered by?

Answer 6

Oral or IV

Question 7

what is the initial load dose and route of furosemide?

Answer 7

IV 40mg

Question 8

How do we assess the efficacy of furosemide?

Answer 8

Improvement of:

1) Tachycardia
2) hypertension
3) O2 requirement
4) increased urinary output
5) monitor weight in long term.

Question 9

How to we ensure safety with furosemide?

Answer 9

Monitor serum Na+, K+ , renal function.