PHARMACOKINETICS OF DISODIUM FOSFOMYCIN IN THE SHRIMP Litopenaeus vannamei Pharmacokinetics of fosfomycin in shrimp

This study examined the pharmacokinetics of a single and three times a day dose of disodium fosfomycin (DF) in shrimp, Litopenaeus vannamei, under controlled laboratory conditions while attempting to reproduce pond conditions. Brackish-like water (salinity 40 g/L) was used at a constant temperature of 26-28 degrees C with water turnover and aeration provided. DF was administered either as a single in-feed dose in the morning at a dose of 250 ppm or three times a day WO, also at a rate of 250 ppm on each dosing. Feed intake was calculated as 3% of biomass and dose rate was calculated as 75 mg/kg of biomass/day or 225 mg/kg/day when administered lid. Peak haemolymph concentration (C-max), time to reach peak (T-max), and elimination half-life (T1/2(beta)) for a single dose of DF were: 1.8 +/- 0.5 mu g/mL; 2.8 +/- 0.4 h, and 0.35 +/- 0.3 h, respectively. After dosing three times per day of DF the same variables were:C-max = 1.7 +/- 0.6 mu g/mL; T-max = 3.0 +/- 1.2 h; and T1/2(beta) = 0.8 +/- 0.2 h, respectively. Muscle and hepato-pancreatic concentrations of DF were only assessed in the shrimp doses three times a day: values reached a maximum concentration of 0.38 mu g/g in muscle and 1.73 mu g/g in hepato-pancreas at 6.2 and 7.5 hours after the first dose. Values in these tissues decreased with a tissue elimination half-life value of 0.21 hours for muscle and 0.783 hours for hepato-pancreas, respectively. The results show that a customized pharmaceutical design is required for this species. Only very sensitive microorganisms could be destroyed with the concentrations of DF shown above and that rapid elimination of DF requires a higher dose at intervals of DF at three times a day dosing.