Pharmacokinetics and metabolism of sulphamonomethoxine in rainbow trout ( Oncorhynchus mykiss) and yellowtail ( Seriola quinqueradiata) following bolus intravascular administration

Abstract

The present study examined the pharmacokinetics and metabolism of sulphamonomethoxine (SMM) in rainbow trout ( Oncorhynchus mykiss) and yellowtail ( Seriola quinqueradiata) after intravascular administration (100 mg kg −1 body weight). Rainbow trout and yellowtail were kept in tanks with running water at 15.0 ± 0.3 °C and running sea water at 21.3 ± 0.2 °C, respectively. Serum concentrations of SMM were determined using high performance liquid chromatography with direct injection. Serum concentrations of SMM in rainbow trout and yellowtail were best described by a two-compartment model. The calculated half-lives for the distribution phase and the elimination phase were 0.43 h and 30.9 h for rainbow trout, and 0.53 h and 5.8 h for yellowtail, respectively. The apparent volume of distribution ( V d ) was larger in rainbow trout ( V d = 0.83 1 kg −1) than in yellowtail ( V d = 0.56 1 kg −1). Total body clearance was calculated as 18.5 ml kg −1 h −1 in rainbow trout and 66.7 ml kg −1 h −1 in yellowtail. The behaviour of N 4-acetyl metabolite, N 4-acetylsulphamonomethoxine (AcSMM), in rainbow trout and yellowtail could be explained well by a one-compartment model. The formation rate constant of the metabolite and the elimination half-lives were 0.0694 h −1 and 15.4 h for rainbow trout, and 0.1896 h −1 and 8.1 h for yellowtail, respectively. Acetylation in rainbow trout and yellowtail was calculated to be 23% and 64%, respectively. The serum protein bindings in vivo of SMM and AcSMM were determined to be 6.4 ± 2.3% and 9.5 ± 3.6% for rainbow trout, and 5.8 ± 1.7% and 6.3 ± 2.3% for yellowtail, respectively.