Comparative Metabolism of Oxolinic Acid by the Rat, Rabbit and Dog

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Abstract
1. The metabolism of oxolinic acid was studied in rats, rabbits and dogs after the oral administration of 10 mg/kg of the 14C-labelled drug. Within 24 h, 18% of the radioactivity had been excreted in the urine from the dog, 27% from the rat and 49% from the rabbit. The faecal radioactivity was 14% from the dog, 35% from the rabbit and 41% from the rat. 2. Small amounts of unconjugated oxolinic acid were found in the urine of all the species as a polar complex. The amount of this complex was much smaller from the dog (0.3%) than from the other species (2–6%). The rabbit excreted far more oxolinic acid glucuronide (14.5%) than did the other species (1.5%). 3. Small amounts of 1-ethyl-1,4-dihydro-7-hydroxy-6-methoxy-4-oxoquino-line-3-carboxylic acid (1–6%) were also found in the urine of every species. In every case one-third to one-fifth of this metabolite was unconjugated, with the remainder excreted as the glucuronide. 4. There was no evidence for the metabolic removal of the ethyl side chain of oxolinic acid.