Plasma and tissue depletion of oxolinic acid after administration to orange-spotted grouper (Epinephelus coioides), snubnose pompano (trachinotus blochii) and giant seaperch (lates calcarifer)

Pharmacokinetics and residues of oxolinic acid (OXO) in serum, muscle, liver, and kidney were measured in orange-spotted grouper Epinephelus coioides, snubnose pompano Trachinotus blochii and giant seaperch Lates calcarifer. Fish were treated with OXO after a single-dose trial (60 mg/kg) by oral gavages and repeat-doses of 60 mg/kg of body weight once daily in feed for five consecutive days. Analysis of OXO kinetic profiles, when determined by HPLC provided elimination half-life in muscle were 131, 26, and 85 h for 26-27 °C orange-spotted grouper, snubnose pompano, and giant seaperch, respectively. Depletion studies were conducted the time for OXO concentrations to fall below 0.1 µg/g (the current tolerance set by the European Medicines Agency (EMA) among fish species establishing an adequate depletion period). The mean tissue OXO concentration in the edible portion was below maximum residue level (MRL) of snubnose pompano at 6 d postdosing, for orange-spotted grouper and giant seaperch, at 10 d postdosing, respectively. When possible, depletion data were fitted to a one-compartment pharmacokinetic model. For all test species, the longest withdrawal period of 9 days in snubnose pompano and 15 days in orange-spotted grouper and giant seaperch were calculated because of a safety span (corresponds to 50% of the time point when at which residues fall below the MRL added to the depletion time). These results suggest withdrawal times with reference to human consumption of treated fish, to establish policy guidelines and basic principles regarding the use of OXO for fish-farming, and to fish-farmers for the proper handling to ensure safe fish that the consumer will not be at risk.