Determination of Pharmacokinetic and Pharmacokinetic-Pharmacodynamic Parameters of Doxycycline against Edwardsiella ictaluri in Yellow Catfish (Pelteobagrus fulvidraco)

This study aimed to examine the pharmacokinetics of doxycycline (DC) in yellow catfish (Pelteobagrus fulvidraco) and to calculate related pharmacokinetic–pharmacodynamic (PK/PD) parameters of DC against Edwardsiella ictaluri. The minimum inhibitory concentration of DC against E. ictaluri was determined to be 500 µg/L. As the increase of oral dose from 10 to 40 mg/kg, the area under the concentration vs. time curve from 0 to 96 h (AUC(0–96)) values were considerably increased in gill, kidney, muscle and skin, and plasma, except in liver. C(max) values exhibited a similar dose-dependent increase trend in plasma and tissues except in liver, but other PK parameters had no apparent dose-dependence. The PK/PD parameter of the ratio of AUC(0–96) to minimum inhibitory concentration (AUC(0–96h)/MIC) was markedly increased in plasma and tissues dose-dependently except in liver, but %T > MIC values were increased only moderately at some dose groups. After receiving the same dose with disparate time intervals from 96 to 12 h, the AUC(0–96h)/MIC was distinctly increased in plasma and tissues, but the %T > MIC had a decreasing trend. When administering 20 mg/kg with a time interval of 96 h, the AUC(0–96h)/MIC values were consistently >173.03 h and the %T > MIC values were above 99.47% in plasma and all tissues. These results suggest that administration of DC at 20 mg/kg every 96 h is a preferable regimen in yellow catfish.