Furazolidone disposition after intravascular and oral dosing in the channel catfish
Abstract1. The pharmacokinetics, tissue distribution and excretion of the nitrofuran drug furazolidone have been examined in the channel catfish. ( 14 C)Furazolidone was administered by intravascular or oral routes in a single dosage of 1 mg/kg body weight. 2. A two-compartment pharmacokinetic model best described parent furazolidone concentrations in the plasma after intravascular dosing. Elimination of parent compound was extremely rapid, with a terminal half-life of 0·27h and total body clearance of 1901ml/h/kg. 3. After oral dosing, furazolidone concentrations in the plasma were highest at 1 h and were below the limit of determination (< 20 ng/ml) at 5 h. The oral bioavailability of parent furazolidone administered in solution was 58%, compared with 28% in a feed mixture. 4. Concentrations of furazolidone and its metabolites were highest in the excretory tissues and lowest in the muscle after oral dosing. Parent furazolidone comprised 10% of the total 14 C in the muscle at 8h and was not detectable (<1 ng/g) at 24h; total 14 C concentrations declined from 274 to 59 ng furazolidone equiv./g between 8 and 168h. Non-extractable (bound) residues comprised 18% of total 14 C in muscle at 8h and 33% at 168h. 5. Renal excretion was the primary route of elimination of 14 C residues and accounted for nearly 55% of the oral dose.