Comparison of pharmacokinetic variables for two injectable formulations of netobimin administered to calves

In a 4 x 4 crossover-design study, pharmacokinetic variables of 2 injectable formulations of netobimin (trisamine salt solution and zwitterion suspension) were compared after SC administration in calves at dosage of 12.5 mg/kg of body weight. Netobimin parent drug was rapidly absorbed, being detected between 0.25 and 12 hours after treatment, with maximal plasma drug concentration (Cmax) values of 2.20 +/- 1.03 micrograms/ml achieved at 0.75 +/- 0.19 hour (trisamine) and 1.37 +/- 0.59 micrograms/ml at 0.81 +/- 0.18 hour (zwitterion). Netobimin area under the plasma concentration-time curve (AUC) was 7.59 +/- 3.11 micrograms.h/ml (trisamine) and 6.98 +/- 1.60 micrograms.h/ml (zwitterion). Elimination half-life (t1/2 beta) was 2.59 +/- 0.63 hours (trisamine) and 3.57 +/- 1.45 hours (zwitterion). Albendazole was not detected at any time. Albendazole sulfoxide was detected from 4 hours up to 20 hours (trisamine) and from 6 hours up to 24 hours (zwitterion) after administration of the drug. The Cmax values were 0.48 +/- 0.16 micrograms/ml and 0.46 +/- 0.26 micrograms/ml for trisamine and zwitterion formulations, respectively, achieved at time to peak drug concentration (Tmax) values of 9.50 +/- 1.41 hours (trisamine) and 11.30 +/- 1.04 hours (zwitterion). Albendazole sulfoxide AUC was 3.86 +/- 1.04 micrograms.h/ml (trisamine) and 4.40 +/- 3.24 micrograms.h/ml (zwitterion); t1/2 beta was 3.05 +/- 0.75 hours (trisamine) and 3.90 +/- 1.44 hours (zwitterion). Albendazole sulfone was detected from 4 (trisamine) or 6 hours (zwitterion) to 24 hours after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)