Abstract
Residual levels of orally administered gentamicin (GM) in the calf kidney were serially determined using the renal biopsy technique. Twelve male calves were given GM per os 1 mg(potency)/kg of body weight twice a day for a week. Three calves were used for serial biopsy which was carried out at 3 hr and 3, 10 and 15 days after the final drug administration. Two calves were sacrificed to collect the kidney samples at each time mentioned above. The renal GM concentration was determined with gentamicin RIA kit, with which more than 95% of GM added was recovered from the renal tissue in vitro and the concentration less than 0.05 μg(potency)/g was detectable in 20 mg of the tissue sample. There was no difference between the renal concentration of GM in the biopsied samples and the samples from the animals sacrificed immediately after the biopsy. The time courses of the decrease in renal drug concentrations were monoexponential in both the serially biopsied samples and the samples from the sacrificed animals. These results suggested that the biopsy technique might have a value for prediction of the withdrawal time of drugs in the food producing animals.
