Ceftiofur distribution in plasma and joint fluid following regional limb injection in cattle

The objective of this study was to evaluate the efficacy of regional intrav enous (i.v.) injection of ceftiofur in delivery of this drug to joint fluid and plasma in a limb distal to a tourniquet in five, healthy, adult, mixed breed beef cattle. A tourniquet was positioned in the mid-metacarpal regio n, and 500 mg of ceftiofur was administered through a catheter in the dorsa l common digital vein (DCDV). Plasma samples were collected from the cathet er at 15, 30 and 45 min postinjection, and from the abaxial proper palmar v ein (APPV) at 15 min postinjection, Synovial fluid was collected from the m etacarpal phalangeal joint at 45 min postinjection. Ceftiofur concentration s were estimated in plasma and synovial fluid using high-pressure liquid ch romatography (HPLC) and a microbiological assay utilizing Pasteurella haemo lytica as the test organism. Both assays indicated highest plasma concentra tions of ceftiofur at 15 min, with the concentrations declining with time. Concentrations of ceftiofur in plasma obtained from the DCDV were not signi ficantly different from APPV levels, indicating rapid distribution of cefti ofur within the limb. Microbiological assay always demonstrated higher conc entrations of ceftiofur compared with HPLC assay, because the former probab ly also detected the active metabolites of ceftiofur as well as the parent compound. At 45 min, ceftiofur concentrations determined by HPLC were 251 /- 97 and 15 +/- 5 mu g/ml, in plasma and synovial fluid, respectively. Reg ional intravenous injection appears to be a feasible technique to produce r apid distribution of ceftiofur within the limb well above therapeutic conce ntrations.