Furazolidone disposition after intravascular and oral dosing in the channel catfish

Abstract

1. The pharmacokinetics, tissue distribution and excretion of the nitrofuran drug furazolidone have been examined in the channel catfish. [¹⁴C]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 ¹⁴C in the muscle at 8h and was not detectable (<1 ng/g) at 24h; total ¹⁴C concentrations declined from 274 to 59 ng furazolidone equiv./g between 8 and 168h. Non-extractable (bound) residues comprised 18% of total ¹⁴C in muscle at 8h and 33% at 168h.

5. Renal excretion was the primary route of elimination of ¹⁴C residues and accounted for nearly 55% of the oral dose.