Transport of furosemide into the intestinal lumen and the lack of effect of gastrointestinal dialysis by charcoal in rats with acute renal failure.

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Abstract
The characteristics of exsorption and/or excretion of furosemide into the small intestinal lumen in rats with acute renal failure (ARF rat) were investigated by an in situ single-pass perfusion technique. The amount of furosemide, which was exsorbed into the intestinal lumen after an intravenous administration of the drug to rats was only very slight. The exsorption rate of the drug was significantly increased in ARF rats as compared with normal rats. The average amount of the drug exsorbed into the perfusate in normal rats was 0.83% of dose, whereas that in ARF rats was 1.83% of dose. The amounts of furosenmide excreted into the bile in normal rats and ARF rats were 1.53% and 2.64%, respectively. The increased exsorption of furosemide in ARF rats appeared to be due primarily to the decreased binding of the drug to the serum protein, because only the unbound drug permeates through the intestinal membrane into the gastrointestinal (g.i.) tact, and, to some extent, to the increased nonrenal excretion caused by poor renal excretion. Oral activated charcoal had little effect on the serum furosemide levels after intravenous administration of the drug at a dose of 10 mg/kg in ARF rats. The lack of effect of activated charcoal on the elimination of the drug may be due to the small amount of the drug excreted into the g.i. tract.