The distribution of oxytetracycline in the tissues of Swine following a single oral dose.

A single oral dose of oxytetracycline hydrochloride (50 mg/kg) produced detectable residues in the following tissues; adrenal, bile, fat, heart, kidney (cortex), kidney (medulla), liver, lung, lymph node (mesenteric), muscle, serum, spleen, thyroid and urine. The highest residue levels were observed in the urine (441 mug/mL) at three hours after administration and they were still present at 48 hours. Maximum serum levels were observed at two hours after administration. Bile samples were positive for inhibitors in all animals sampled. Drug residues were not detected in spleen, thyroid, lymph node, adrenals and heart at 48 hours.Drug levels in important edible tissues were expressed as a percentage of drug levels in two tissues with high drug concentrations - urine and kidney cortex. The percentages were highly variable when compared with urine and much less variable when compared to kidney cortex.Kidney cortex appears to be an excellent tissue for drug residue monitoring.