Pharmacokinetics of nalidixic acid and sodium nifurstyrenate in cultured fish following bolus intravascular administration

The present study examined the pharmacokinetics of nalidixic acid (NA) in rainbow trout (Oncorhynchus mykiss) and sodium nifurstyrenate (NFS) in yellowtail (Seriola quinqueradiata) after a bolus intravascular administration. The doses of NA and NFS were 20 mg/kg and 10 mg/kg body weight, respectively. Rainbow trout were kept in tanks with running fresh water at 15.0 ±0.3deg;C. Yellowtail were kept in tanks with running sea water at 21.3±0.2deg;C. Serum concentrations of NA and NFS were determined using high performance liquid chromatography. Serum concentrations of NA in rainbow trout and NFS in yellowtail were best described by a two-compartment open model. The half-lives for the distribution phase (T1/2α) and elimination phase (T1/2β) were 1.4 h and 13 h for NA in rainbow trout and 0.6 h and 7.7 h for NFS in yellowtail, respectively. The apparent volume of distribution (Vd) and total body clearance (ClB) were estimated to be 1.01 l/kg and 54.7 ml/kg/h for NA in rainbow trout and 2.99l/kg and 271 ml/kg/h for NFS in yellowtail, respectively. The serum protein bindings in vivo were determined to be 10.9 ± 4.0% for NA in rainbow trout and 69.4± 7.5% for NFS in yellowtail, respectively. As an application of this pharmacokinetic study, the oral bioavailability and the dosage regimens of NA in rainbow trout and NFS in yellowtail were briefly evaluated.