The effect of breed and sex on sulfamethazine,enrofloxacin, fenbendazole and flunixin meglumine pharmacokinetic parameters in swine

Drug use in livestock has received increased attention due to welfare concerns and food safety. Characterizing heterogeneity in the way swine populations respond to drugs could allow for group‐specific dose or drug recommendations. Our objective was to determine whether drug clearance differs across genetic backgrounds and sex for sulfamethazine, enrofloxacin, fenbendazole and flunixin meglumine. Two sires from each of four breeds were mated to a common sow population. The nursery pigs generated (n = 114) were utilized in a random crossover design. Drugs were administered intravenously and blood collected a minimum of 10 times over 48 h. A non‐compartmental analysis of drug and metabolite plasma concentration vs. time profiles was performed. Within‐drug and metabolite analysis of pharmacokinetic parameters included fixed effects of drug administration date, sex and breed of sire. Breed differences existed for flunixin meglumine (P‐value<0.05; Cl, Vd_ss) and oxfendazole (P‐value<0.05, AUC_0→∞). Sex differences existed for oxfendazole (P‐value < 0.05; T_max) and sulfamethazine (P‐value < 0.05, Cl). Differences in drug clearance were seen, and future work will determine the degree of additive genetic variation utilizing a larger population.