Disposition of oral sulfathiazole was studied in swine. Pigs were slau
ghtered 6, 12, 24, and 48 h after an oral dose of [C-14]sulfathiazole
(two at each time period). Excretion of C-14 was rapid (>90% in 48 h),
primarily via the urine. Metabolites isolated and characterized by H-
1 NMR and FAB MS were N-4-acetylsulfathiazole from urine, kidney, live
r, blood, and muscle; N-4-glucoside of sulfathiazole from muscle; and
an apparent diconjugate from liver, a glucuronide of N-4-acetylsulfath
iazole. Quantitation was accomplished by HPLC analysis of samples (ext
racts of tissue and urine) spiked with the reference compounds. Peaks
corresponding to the retention time of the reference compounds were tr
apped and assayed for C-14. Sulfathiazole and N-4-acetylsulfathiazole
were the principal C-14-labeled compounds in urine and kidney. If pres
ent, the glucoside or glucuronide represented <5% of the C-14 in urine
. Liver and muscle contained significant amounts of sulfathiazole, N-4
-acetylsulfathiazole, and N-4-glucoside of sulfathiazole. Quantitation
of the diconjugate was not attempted. The amounts isolated suggest it
was a minor metabolite; however, instability during isolation was app
arent. On the basis of the results, liver, kidney, and urine are poten
tial target tissues for a residue monitoring program and the nature of
the metabolite present in the tissue must be considered when an assay
procedure is selected.