Comparative Pharmacokinetic of Three Sulfadiazine Suspensions by Oral Administration in Chickens

The chemotherapeutics, sulfadiazine (SDA) and trimethoprim (TMP), are extensively used in a variety of animal species. In this study, a pharmacokinetic analysis was performed to compare the bioequivalence of a combined SDA and TMP product against existing licensed SDA and TMP formulations in broiler chickens. Three groups of 15 birds were administered a single dose of either the test formulation or a reference oral suspension. The plasma concentration of SDA and TMP were determined by reverse-phase high performance liquid chromatography (HPLC), and the maximal plasma concentration (Cmax), area under the curve (AUC), the peak time (Tmax), mean residence time (MRT) and elimination half-life (T1/2), were calculated for SDA. The combined formulation I and II reference suspension exhibited almost identical concentration-time curves, and ANOVA analyses of the pharmacokinetic parameters identified no significant differences between the reference preparations and the test one. Furthermore the AUC and Cmax values of the SDA active ingredient were not significantly different. The I formulation was bioequivalent with both II and III (80-125% and 70–143%, respectively, at the 90% confidence interval). In conclusion, the combined SDA and TMP product was bioequivalent with both existing commercially available SDA suspensions and can be used interchangeably in veterinary medical practice.