Metabolism of Indanyl Carbenicillin by Dogs, Rats, and Humans

Indanyl carbenicillin, an ester of carbenicillin with indanol, is absorbed in the intestine after oral administration and is subsequently hydrolyzed to release the parent antibiotic which can be measured in serum and urine. To study the metabolism of indanyl carbenicillin, labeled indanol was prepared by exchange with tritiated water and was used, with phenylmalonyl chloride and 6-aminopenicillanic acid, to prepare labeled indanyl carbenicillin. Labeled indanol and indanyl carbenicillin were orally administered to dogs and rats with good recovery of label in the urine. In the dog, indanol, whether administered as such or as indanyl carbenicillin, was excreted in the urine as the glucuronide and sulfate ester conjugates of indanol and as conjugates of two hydroxyindanones and two hydroxyindanols, as determined by combined gas chromatography-mass spectrometry. Rats, conversely, excreted only the conjugates of indanol, whether indanol or indanyl carbenicillin was administered. After oral administration of unlabeled indanyl carbenicillin to humans, conjugates of indanol were recovered in the urine in excellent yield, as determined by a gas chromatographic assay. None of the other indanol metabolites formed by the dog was observed in human urine.