Pharmacokinetics and residue elimination of cynatratoside-C in the grass carp Ctenopharyngodon idellus following a single intraperitoneal injection

Abstract

Cynatratoside-C, isolated from Cynanchum atratum, is a promising alternative agent for the control of the ecoparasite Ichthyophthirius multifiliis. However, the pharmacokinetics and residue elimination of cynatratoside-C in fish have yet to be reported. Here, we aimed to investigate the pharmacokinetics and residue elimination of cynatratoside-C in grass carp following a single intraperitoneal (i.p.) dose of 2 mg/kg body weight at a water temperature of 23.0 ± 0.3 °C. The concentrations of cynatratoside-C in the serum, liver, kidney, and muscle were determined using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). We found that the pharmacokinetics of cynatratoside-C in the grass carp was described by a two-compartment model. The absorption half-life (t1/2Kα), distribution half-life (t1/2α), and elimination half-life (t1/2β) of cynatratoside-C in the serum were 0.28 h, 1.45 h, and 69.32 h, respectively. The maximum cynatratoside-C concentration (Cmax) in the serum was 123.81 μg/L, with a time to peak concentration (Tmax) of 0.5 h. The post-injection residue concentration of cynatratoside-C (during the elimination period) was highest in the liver and lowest in the muscle. The concentration of cynatratoside-C in the muscle fell below the limit of quantification (1.24 ng/g) 15 days post-administration. Thus, for grass carp, we recommend a withdrawal period of 15 days following a single i.p. dose of 2 mg cynatratoside-C/kg body weight at a water temperature of 23.0 ± 0.3 °C.