Multiple-dose pharmacokinetic study of flumequine in Atlantic salmon ( Salmo salar L.)

Abstract

Medicated feed pellets containing flumequine (5 g/kg) were given to a group of sea-water-adapted Atlantic salmon ( Salmo salar L.). The pellets contained small glass X-ray-dense beads. The fish were offered a fixed quantity of medicated feed during a period of 6 or 8 consecutive days. A control group received non-medicated pellets. Feed intake was assessed by counting the number of beads on X-ray pictures taken of the sampled fish. The results show that almost all the offered feed was eaten by the fish. No difference in appetite could be detected between the medicated and non-medicated feed groups. Plasma samples were taken each day of the medication period and for 8 days following medication. Tissue samples (liver, muscle and skin) were taken every 2nd day. A steady-state level of flumequine in plasma, liver and muscle tissue was achieved on the 3rd day of medication. The estimated elimination half-life in plasma, liver and muscle tissue was about 21 h. Half-life in skin tissue was approx. 33 h, and therefore it took longer to reach a steady-state level. Skin tissue data show an accumulation of flumequine during the medication period ranging from 14 μg/g on the 2nd day to 26 μg/g on the 8th day. The highest flumequine concentrations were observed in skin tissue and liver tissue. Flumequine level in muscle tissue was approx. half that found in skin tissue. Water temperature remained approx. 8°C during the whole experiment. The flumequine concentrations observed should give good protection against the most common pathogenic bacteria in European fish farming, which can be concluded by comparison with minimal inhibitory concentrations (MICs) as listed in literature.