Vaccination mitigates the impact of PRRS v infection on the pharmacokinetics of ceftiofur crystalline‐free acid in pigs

The pharmacokinetics of intramuscularly administered ceftiofur crystalline‐free acid ( CCFA ) were determined in pigs that were clinically healthy ( n = 8), vaccinated with a Porcine reproductive and respiratory syndrome modified live virus ( PRRS MLV ) ( n = 10), challenged with wild‐type porcine reproductive and respiratory syndrome virus ( PRRS v) VR ‐2385 ( n = 10), or vaccinated with PRRS MLV and later challenged with wild‐type PRRS v VR ‐2385 ( n = 10). Animals were given a single dose of CCFA intramuscularly at 5 mg/kg body weight. Blood was collected at 0 (pretreatment), 0.25, 0.5, 1, 6, 12, 24, 48, 96, 144, 192, and 240 h postinjection. Plasma was analyzed using liquid chromatography‐mass spectrometry. Plasma concentration–time curves for each group were evaluated with noncompartmental modeling. When compared to control animals, those receiving the PRRS v wild‐type challenge only had a lower AUC 0‐last , higher Cl/F, and higher Vz/F. The PRRS v wild‐type challenge only group had the longest T 1/2 λ . The C max did not differ among all four treatments. Control animals had no statistically significant differences from animals vaccinated with PRRS MLV alone or animals vaccinated with PRRS MLV and later challenged with wild‐type PRRS v. Our results suggest that PRRS v wild‐type infection has the potential to alter CCFA pharmacokinetics and PRRS MLV vaccination may attenuate those changes.