The oral pharmacokinetics of diclofenac (DF) were evaluated in cattle by analyzing plasma
concentration-time data after its intravenous and oral administration in order to propose
the oral administration of DF as effective route to avoid long withdraw period. DF was
intravenously and orally administered at 1 mg/kg to cattle using a crossover design with a
4-week washout period. Plasma concentrations of DF were determined by a HPLC analysis. The
mean absorption time (MAT) and absorption half-life (t1/2ka) were 1.61 ± 0.61
and 1.51 ± 0.38 hr, respectively, and bioavailability was nearly 100%. The oral
pharmacokinetics of acetaminophen (AAP) were also evaluated in cattle. Plasma
concentrations of AAP were determined by a HPLC analysis. MAT and t1/2ka were
2.85 ± 0.93 and 1.53 ± 0.28 hr, respectively, and bioavailability was approximately 70%.
In conclusion, the results of the present study indicate that DF and AAP are rapidly
absorbed from the forestomach of cattle. Therefore, the appropriate efficacies of these
drugs may be achieved via their oral administration, even in cattle.