Enrofloxacin pharmacokinetics and tissue distribution in Takifugu flavidus after oral administration at three salinity levels

Rongrong Maa,b,c, Tao Rena, c, Ping Zhuangb, Wenhong Fangb, Xian le Yanga, Kun Hua*
aNational Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, Shanghai 200090, P.R. China
bEast China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Key Laboratory of Yangtze Estuary Fishery Ecology. Shanghai 200090, P.R. China
Kun Hu, Ph.D.
National Pathogen Collection Center for Aquatic Animals, Shanghai Ocean University, 999 Huchenghuan Road, Lingang New City Shanghai 201306, P. R. China.
Tel: 86-21-61900453, Fax: 86-21-61900453;
E-mail: khu@shou.edu.cn

Background: Enrofloxacin is an effective drug for the treatment of bacterial diseases in aquatic animals. Its pharmacokinetics in fish may vary with species and water environment. The present study was designed to explore the pharmacokinetics and tissue distribution of enrofloxacin in Takifugu flavidus at different salinity levels (10‰, 20‰ and 30‰). The concentrations of enrofloxacin in plasma and tissues (kidney, liver and muscle) in T. flavidus after a single oral dose of 10 mg/kg were simultaneously determined by HPLC. The parameters in plasma and tissues were calculated by classical compartmental model analysis, and their concentration-time curves were fitted by the two-compartment open-pharmacokinetic model.

Results: At 10‰ salinity, the peak levels of enrofloxacin in plasma, liver, kidneys and muscles were 15.20 μg/mL, 3.00 μg/g, 29.18 μg/g and 0.58 μg/g, respectively. The elimination half-lives (t1/2β) of enrofloxacin in the corresponding tissues were 78.77 hours, 86.95 hours, 287.03 hours and 61.86 hours, correspondingly. AUC0-∞ in these tissues were 958.68 μg·h/mL, 188.30 μg·h/g, 1640.88 μg·h/g and 72.896 μg·h/g, respectively.

Conclusion: These findings indicate that drug concentrations in tissues with higher salinity were more elevated, except for the kidneys. The kidneys might be the main organs of excreting and metabolizing drugs in tawny puffer, and the functions of kidneys are probably limited to conducting enrofloxacin elimination with higher salinity level. In addition, a single-dose oral administration of 10 mg/kg of enrofloxacin was sufficient to obtain therapeutic blood concentrations in tawny puffer at different salinity rates.