Quick Review on Lasix (furosemide)

Lasix (Furosemide) is a loop diuretic that we use very commonly in the ICU. It is most often use in acute decompensated heart failure leading to pulmonary edema. Not only does Lasix work at the loop of Henle by blocking the reabsorption of sodium, potassium, chloride, and excess fluid, it also has direct pulmonary venodilation activity. In fact this activity of venodilation occurs first, within 15 minutes of administration. Increase in urine output typically starts 30 minutes after administration. This venodilation can lead to hypotension but also symptom relief from reducing pulmonary vasocongestion. Other commonly used loop diuretics include bumetanide, torsemide, and ethacrynic acid.

In acute situations, it is given as an IV medication, but patients can commonly be on this medication at home taking it by mouth (PO). The PO to IV conversion is 2:1. So Lasix 40mg PO converts to 20mg IV. It is usually given as bolus doses but can also be administered as an effusion. Its effect typically lasts 6 hours, which can be remembered by its name (“LAsts SIX hours”).

The most common side effect of lasix is low potassium (hypokalemia), requiring frequent electrolyte checks and replacement when dosing Lasix frequently. The most severe side effect that occurs with very high doses is ototoxicity. This can potentially end up causing permanent hearing loss.

One last interesting fact: Lasix is on both the WHO’s list of essential medications and also the banned list of drugs for athletic competitions due to concerns that it can mask the presence of other performance-enhancing drugs.

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