Pharmacokinetics of long-acting cefovecin in copper rockfish (Sebastes caurinus)

To assess the pharmacokinetic properties of cefovecin in a cold-water teleost species.

10 healthy adult copper rockfish (Sebastes caurinus), sex unknown.

Cefovecin (16 mg/kg) was administered SC to the rockfish. Blood samples were collected at predetermined points for measurement of plasma cefovecin concentrations (3 samples/fish). Plasma cefovecin concentrations were measured via liquid chromatography with mass spectrometry. Pharmacokinetic analysis was performed by means of naïve pooled analysis and compartmental modeling. Plasma protein binding of cefovecin was determined by ultrafiltration.

Cefovecin administration appeared to be well tolerated by the rockfish. Pharmacokinetic analysis resulted in a maximum plasma concentration of 104.8 μg/mL at 2.07 hours after administration. Plasma terminal half-life was 32.5 hours, and area under the curve was 5,132 h·g/mL. Plasma protein binding was low (< 10%) for plasma concentrations of 10 and 100 μg of cefovecin/mL when assessed at 7.8° and 20°C. Plasma concentrations > 1 μg/mL persisted for the full 7-day follow-up period.

SC administration of cefovecin to copper rockfish at a dose of 16 mg/kg yielded plasma concentrations > 1 μg/mL that persisted to 7 days, but some interindividual variability was observed. The low degree of plasma protein binding but high circulating concentration of free drug may allow an extended administration interval in rockfish. Studies are needed to assess the efficacy and safety of this dose in rockfish.