Furosemide
Furosemide. Loop diuretic — inhibits Na+/K+/2Cl- cotransporter (NKCC2) in thick ascending limb of loop of Henle. Most potent class of diuretic… Oral half-life 0.6 h.
Loop diuretic — inhibits Na+/K+/2Cl- cotransporter (NKCC2) in thick ascending limb of loop of Henle. Most potent class of diuretic; cornerstone of CHF / pulmonary edema management. Ototoxicity at high IV bolus doses.
PK: THE RECORD ERASED ITS OWN FLIP-FLOP SIGNAL. Its citation states 0.6 h intravenously and 0.8 h orally, and the record stored 0.8 on BOTH rows — so the disposition half-life was replaced by an absorption-limited one, which is confirmed elsewhere as "absorption rate-limited kinetics of furosemide". One value of 0.6 h now serves both routes. V 14 L was unsourced; the true steady-state volume measured after an intravenous bolus is 8.3 L, and it cross-checks with the same paper clearance to within about 2%. F is corrected to the tablet fasting figure of 51%, with the 40 to 51% spread recorded, since bioavailability here is genuinely formulation- and product-dependent. A PLASMA MODEL DOES NOT REPRESENT THIS DRUG EFFECT and must never be given one: furosemide acts from the luminal side of the nephron, so the driver is urinary excretion rate, the excretion-response curve shows clockwise hysteresis indicating acute tolerance within a single dose, and a three-fold difference in delivered drug produced no difference in diuresis. The intramuscular route is removed as never studied.
Pharmacokinetics
- Oral — t½ 36 min · F 51% · Vd 8.3 L
- IV — t½ 36 min · F 100% · Vd 8.3 L
Sources: PMID:3370062, PMID:6723758, PMID:3999028