Pharmacokinetic profiles of netobimin metabolites after oral administration of zwitterion and trisamine formulations of netobimin to cattle.

Pharmacokinetic profiles of the major metabolites of netobimin were investigated in calves after oral administration of the compound (20 mg/kg) as a zwitterion suspension and trisamine salt solution in a two-way cross-over design. Blood samples were taken serially over a 72-h period and plasma was analysed by HPLC for netobimin (NTB) and its metabolites, including albendazole (ABZ), albendazole sulphoxide (ABZSO) and albendazole sulphone (ABZSO2). NTB was occasionally detected in plasma between 0.5 and 1.0 h post-treatment. ABZ was not detectable at any time. ABZSO was detected from 0.5-0.75 h up to 32 h post-administration, with a Cmax for the zwitterion suspension of 1.21 +/- 0.13 micrograms/ml and AUC of 18.55 +/- 1.45 micrograms.h/ml, respectively, which were significantly higher (P less than 0.01) than the Cmax (0.67 +/- 0.12 micrograms/ml) and AUC (8.57 +/- 0.91 micrograms.h/ml) for the trisamine solution. ABZSO2 was detected in plasma between 0.75 and 48 h post-administration. The zwitterion suspension resulted in a Cmax (2.91 +/- 0.10 micrograms/ml) and AUC (51.67 +/- 1.95 micrograms.h/ml) for ABZSO2, which were significantly higher (P less than 0.01) than those obtained for the trisamine solution (Cmax = 1.67 +/- 0.11 micrograms/ml and AUC = 22.77 +/- 1.09 micrograms.h/ml). The ratio of AUC for ABZSO2/ABZSO was 2.92 +/- 0.26 (zwitterion) and 2.80 +/- 0.20 (trisamine). The MRT for ABZSO2 was significantly longer (P less than 0.01) after treatment with the zwitterion suspension than after treatment with the trisamine solution.(ABSTRACT TRUNCATED AT 250 WORDS)