Endometrial Tissue and Blood Plasma Concentration of Ceftiofur and Metabolites After Intramuscular Administration of Ceftiofur Crystalline-Free Acid to Mares
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Intramuscular administration of ceftiofur crystalline–free acid at the label dose will exceed the minimum inhibitory concentration (MIC) for Streptococcus equi subs. zooepidemicus in the equine endometrium.
1. Introduction
Systemic administration of ceftiofur crystalline–free acid (CCFA),a licensed for use in the horse, may be a potential treatment for Streptococcus zooepidemicus bacterial endometritis in mares.
2. Materials and Methods
Three mares were administered a single dose of CCFA (6.6 mg/kg IM), and blood and endometrial biopsies were collected at predetermined intervals for 144 hours. Six additional mares received CCFA at times 0, 4, 11, and 18 days and were monitored and sampled (5 mares had blood samples only for 49 days; 1 mare had blood and endometrial tissue sampled for 25 days). Samples were tested by HPLC/MS/MS for ceftiofur and metabolites (DCA) concentrations.
3. Results
A mean ceftiofur concentration of 0.367 ± 0.0162 μg/mL (mean ± SEM) was detected at 96 hours after administration and plasma levels surpassed the CLSI reported minimum inhibitory concentration (Clinical Laboratory Standards Institute reported MIC) for S. zooepidemicus of 0.25 g/mL through 96 hours. Mean endometrial tissue concentration was 0.510 ± 0.0418 μg/g at 96 hours and remained above the MIC throughout the 144- hour monitoring period. Mares administered multiple doses of CCFA maintained plasma and endometrial tissue levels above the MIC at most data collection points.
4. Discussion
CCFA, using label dosage, should be effective in the treatment of equine bacterial endometritis caused by S. zooepidemicus and other susceptible bacterial pathogens in the horse.
Funding and CCFA (ExcedeTM) were provided by Pfizer Animal Health.
All HPLC/MS/MS was performed at the Pharmacology Core Laboratory, Colorado State University.
Footnote
a Excede, Pfizer Pharmacia & Upjohn Co., New York, NY 10017.
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Affiliation of the authors at the time of publication
961 Cayots Corner Road, Chesapeake City, MD 21645 (Scofield); Department of Clinical Sciences (Black, Wittenburg, Gustafson, Ferris, Hatzel, Traub-Dargatz, McCue); and Department of Animal Sciences (Black), Colorado State University, Fort Collins, CO 80523, USA
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