Aspects of the Pharmacokinetics of Albendazole Sulphoxide in Sheep

The plasma disposition kinetics of albendazole sulphoxide (ABZSO), ((+)ABZSO and (–)ABZSO) and its sulphone metabolite (ABZSO₂) were investigated in adult sheep. Six Corriedale sheep received albendazole sulphoxide by intravenous injection at 5 mg/kg live weight. Jugular blood samples were taken serially for 72 h and the plasma was analysed by high-performance liquid chromatography (HPLC) for albendazole (ABZ), ABZ sulphoxide (ABZSO) and albendazole sulphone (ABZSO₂). Albendazole was not detected in the plasma at any time after the treatment, ABZSO and ABZSO₂ being the main metabolites detected between 10 min and 48 h after treatment. A biexponential plasma concentration versus time curve was observed for both ABZSO and ABZSO₂ following the intravenous treatment. The plasma AUC values for ABZSO and ABZSO₂ were 52.0 and 10.8 (g.h)/ml, respectively. The ABZSO₂ metabolite was measurable in plasma between 10 min and 48 h after administration of ABZSO, reaching a peak concentration of 0.38 g/ml at 7.7 h after treatment. Using a chiral phase-based HPLC method, a biexponential plasma concentration versus time curve was observed for both ABZSO enantiomers. The total body clearance was higher for the (–) than for the (+) enantiomer, the values being 270.6 and 147.75 (ml/h)/kg, respectively. The elimination half-life of the (–) enantiomer was shorter than that of the (+) enantiomer, the values being 4.31 and 8.33 h, respectively. The enantiomeric ratio (+)ABZSO/(–)ABZSO at t ₀ was close to unity. However, the ratio in the plasma increased with time.