LAUSR

Abstract The absorption and depletion of dietary administered praziquantel (PZQ) were explored in greater amberjack, Seriola dumerili, a promising farmed fish species in the Mediterranean area and elsewhere. Greater amberjack weighing 84 g were fed once daily for 5 days on diets containing either 1.5 or 3.0 g/kg of PZQ to deliver dose rates of 30 or 60 mg/kg fish, respectively. During the first day, plasma samples were measured for PZQ concentration at 2, 4, 8 and 24 h post-feeding. On the other treatment days, blood (plasma), muscle plus skin and gills were collected daily 24 h post-administration. Praziquantel was rapidly absorbed into fish circulation as the maximum plasma concentration (Cmax) was achieved at 8 h (3.0 μg/ml) and 2 h post administration (4.3 μg/ml) for the low and high dosing, respectively. The two-fold increase in dosing led to a significant dose-dependent effect between the mean PZQ concentrations of the two dosing regimens in most selected sampling points such as 2, 4, 24, 120 h. While the elimination half-life (t1/2b) was shorter in high PZQ dosing (8.2 h) compared to that calculated for the low (15.1 h), depletion of PZQ from greater amberjack plasma was considered rapid on both trials, as its concentration fell to 0.31 (low) and 0.56 (high) μg/ml 24 h post-treatment. Elimination of PZQ was also rapid from the gills and muscle plus skin, with drug levels measured below the limit of quantification as early as 72 and 96 h post treatment, for the low and the high dosing, respectively. Overall, the high dosing regimen is preferable over the low dosing schedule since it was readily accepted and resulted in higher circulatory levels in greater amberjack. Moreover, the rapid elimination of PZQ from the body compartment of greater amberjack suggested a twice a day administration of medicated meals to ensure adequate drug circulatory levels.