MULTIPLE ROUTE AND DOSE PHARMACOKINETICS OF ENROFLOXACIN IN JUVENILE ATLANTIC SALMON

The fluoroquinolone antibacterial family is a relatively recent group of bactericidal compounds, generally characterized by efficacy against a wide spectrum of bacterial organisms and exhibiting minimal adverse effects in treated patients, The fluoroquinolones are widely prescrib ed in both human and veterinary medicine, though in veterinary medicin e in the USA there are currently only two approved compounds, enroflox acin (Baytril(R), Bayer Animal Health, Shawnee Mission, KS) and sarafl oxacin (SaraFlox(R), Abbott Laboratories, North Chicago, IL), both wit h limited species and disease label approvals, Currently, there are no approved fluoroquinolone antibacterials to treat bacterial infectious diseases in cultured fish species. Enrofloxacin was administered to j uvenile Atlantic salmon as a single bolus via intraarterial (i.a.), in traperitoneal (i.p.), intramuscular (i.m.), or oral gavage routes of a dministration, The drug was administered via the first three routes to achieve a dose of 10 mg/kg, and via oral gavage to achieve both 10 (p .o.-10) and 5 (p.o.-5) mg/kg doses. Two-compartment model kinetics wer e observed with elimination of half-lives (t(1/2)) of 130.6, 34.32, 84 .98, 105.11, and 48.24 h, area under the drug concentration-time curve s (AUG) of 84.3, 75.31, 55.61, 41.68, and 38.81 mu g.h/mL, and bioavai labilities (F) of 100, 89.34, 65.97, 49.44, and 46.04% (i.a., i.p., i. m,, p.o.-10, p.o.-5, respectively). All administration routes at 10 mg /kg were found to yield comparable drug concentration-time curves for multiple tissue, indicating no distinct advantage of using one route o ver another from a kinetics perspective. Finally, the 5 mg/kg dose (p. o.-5) yielded comparable multiple tissue drug concentration-time curve s to the 10 mg/kg dose (p.o.-10), providing pharmacokinetic evidence t o justify therapeutic efficacy trials with the lower dose.