Multiple-dose pharmacokinetic and depletion studies of sarafloxacin in Atlantic salmon, Salmo salar L.

Abstract. Two multiple-dose pharmacokinetic and depletion studies with sarafloxacin hydrochloride in feed pellets were conducted with Atlantic salmon at 12.1 ± 1.1 ?C and 9.3 ± 1.5?C, respectively. The dose regimens used were 10mg sarafloxacin kg^-1 biomass for 10 days, and 20mg sarafloxacin kg^-1 biomass for 5 days. In the 10-day study, the highest average concentrations of sarafloxacin in plasma, muscle and liver were 0.14, 0.39 and 0.88μgg(ml)^-1, respectively. In the 5-day study, the highest average concentrations in plasma, muscle, liver and skin were 0.40, 0.61, 1.56 and 0.19μg(ml)^-1, respectively. A comparison between the individual plasma concentrations and the corresponding tissue concentrations revealed significantly higher concentrations in tissue than in plasma during the depletion phase. A similar comparison made in the therapeutic phase from 3 days after first medication to one day after the last medication revealed significantly higher concentrations in liver and muscle than in plasma, and significantly lower concentrations in skin than in plasma. On withdrawal of the drug, sarafloxacin concentrations in plasma and the different tissues declined rapidly, Sarafloxacin was not detected in any plasma sample taken 6 days or more after the end of medication. The corresponding figures for muscle, skin and liver tissues were 14, 20 and 22 days, respectively. The half-lives of sarafloxacin varied in the different tissues included in the studies. The half-life was shortest in plasma, and increased in ascending order in muscle, liver and skin.