Q: Natriuresis from oral furosemide is lower than the intravenous (IV) furosemide?
Although oral furosemide is half potent than IV furosemide natriuresis effect is the same.
This is due to the reason that the plasma diuretic concentrations stay sustained above the diuretic threshold for a longer period of time with oral form, and causes the same level of natriuresis as the IV dose.
To complicate the matter, there is a huge variability in the degree of bioavailability of oral furosemide between different patients with same kidney functions and even within the same patient at different times.
1. Kaojarern S, Day B, Brater DC. The time course of delivery of furosemide into urine: an independent determinant of overall response. Kidney Int 1982; 22:69.
2. Ellison DH, Felker GM. Diuretic Treatment in Heart Failure. N Engl J Med 2017; 377:1964.