A sensitive, precise, and efficient analytical method for
sulfamethazine in the liver, kidney, heart, skeletal muscle, and fat of lambs is reported. The method involves freezing cubed tissue in liquid
nitrogen, powdering the frozen tissue in a liquid
nitrogen-cooled blender, and extracting the tissue on a
sodium sulfate column with
chloroform:
acetone. A thin-layer chromatographic procedure capable of separating and quantitating
sulfamethazine and 3 metabolites (acetyl, hydroxylated, and polar conjugate(s) in lamb urine is also reported.
Sulfamethazine was administered intravenously (107.25 mg/kg
body weight) to 14 cross-bred ewe lambs. The concentration of
sulfamethazine in plasma and tissues and
sulfamethazine and its metabolites in urine were determined in samples collected at specific postdosing times. The concentration of
sulfamethazine in plasma exceeded 5 mg/100 ml for 18 to 24 hours after
drug administration. The excretion of diazotizable materials in the urine was essentially complete at the 60th hour after dosing. The
drug was excreted in the urine as
sulfamethazine, a hydroxylated metabolite, acetylsulfamethazine, and polar conjugate(s). Tissue concentrations of the
drug were greatest in the kidney and less (in decreasing quantities) in liver, heart, skeletal muscle, body fat, and omental fat.