Pharmacokinetics of oxolinic acid in the Pacific white shrimp (Litopenaeus vannamei) and in vitro antimicrobial activity on Vibrios

The pharmacokinetics and tissue elimination of oxolinic acid (OA) in the Pacific white shrimp, Litopenaeus vannamei, were investigated following oral administration via feed by HPLC method. The minimum inhibitory concentrations (MIC) of OA on the pathogenic Vibrio were detected. The Pharmacokinetics/ pharmacodynamics (PK/PD) parameters were calculated, and dosage regime and withdrawal time were developed. The haemolymph OA concentration vs. time after oral administration via feed was best described by a twocompartment model with first absorption following a single dose of 30 mg/kg. The peak concentration (C_max), peak time (T_max), area under curve (AUC_0-24) and elimination half-life time (t_1/2z) for hemolymph were 14.70 mg/L, 2 h 244.6 mg/L, and 18.56 h, respectively. Peak concentrations(C_max)in muscle, hepatopancreas and gill were 4.11 mg/kg, 17.20 mg/kg and 7.01 mg/kg, respectively; elimination half-life time (t_1/2z) were 10.71 h, 12.31 h and 16.75 h, respectively. The OA MICs of 132 Vibrios isolates varied mainly from 0.15 to 1.25 μg/mL with MIC₅₀ of 0.62 μg/mL and MIC₉₀ of 1.25 μg/mL. The ratios of C_max/MIC₉₀ and AUC_0-24/MIC₉₀, which were two important indices for PK/PD relationship, were 11.76 and 195.7, respectively. The results showed that OA dosage of 30 mg/kg by medicated feed could effectively combat bacterial diseases caused by the Vibrios.