Plasma pharmacokinetics of melamine and a blend of melamine and cyanuric acid in rainbow trout (Oncorhynchus mykiss)

The objective of the study was to obtain pharmacokinetic parameters for melamine and blend of melamine (MEL) and cyanuric acid (CYA) in rainbow trout (Oncorhynchus mykiss). The single target dosage of MEL (20mg/kg bw) and the blend of MEL and CYA (5 and 1.67 mg/kg bw, respectively) were designed and plasma samples were collected at 30 min, 1, 4, 8, 12, 20, 24, 36, 48, 72, 144 and 240 h sequentially. An optimized method for simultaneous determination of MEL and CYA in plasma and animal tissues by LC-MS/MS was used. The data were shown to best fit a non-compartment model with first order processes of linear characters for melamine, with half-life (t(½)) of 32.2-32.9h, clearance (Cl(z/F)) of 35.9-36.6 ml/h/kg, and volume of distribution (V(ss)) of 1.67-1.74 l/kg. Withdrawal of CYA was much more rapid than that of MEL with higher Cl(z/F) (783.56 ml/h/kg) and shorter t(½) (7.92 h). T(max) of MEL20 and MEL5 were 12 and 20 h, respectively, which showed that T(max) of MEL5 was delayed when MEL and CYA were given together. The results are quite different from those in mammals and showed much slower elimination of MEL and CYA from rainbow trout body.