FURAZOLIDONE DISPOSITION AFTER INTRAVASCULAR AND ORAL DOSING IN THE CHANNEL CATFISH

1. The pharmacokinetics, tissue distribution and excretion of the nitr ofuran drug furazolidone have been examined in the channel catfish. [C -14]Furazolidone was administered by intravascular or oral routes in a single dosage of 1 mg/kg body weight. 2. A two-compartment pharmacoki netic model best described parent furazolidone concentrations in the p lasma after intravascular dosing. Elimination of parent compound was e xtremely rapid, with a terminal half-life of 0.27 h and total body cle arance of 1901 ml/h/kg. 3. After oral dosing, furazolidone concentrati ons in the plasma were highest at 1 h and were below the limit of dete rmination (< 20 ng/ml) at 5 h. The oral bioavailability of parent fura zolidone administered in solution was 58%, compared with 28% in a feed mixture. 4. Concentrations of furazolidone and its metabolites were h ighest in the excretory tissues and lowest in the muscle after oral do sing. Parent furazolidone comprised 10% of the total C-14 in the muscl e at 8 h and was not detectable (<1 ng/g) at 24 h; total C-14 concentr ations declined from 274 to 59 ng furazolidone eguiv./g between 8 and 168 h. Non-extractable (bound) residues comprised 18% of total C-14 in muscle at 8 h and 33% at 168 h. 5. Renal excretion was the primary ro ute of elimination of C-14 residues and accounted for nearly 55% of th e oral dose.