Enrofloxacin is a concentration-dependent fluoroquinolone with antimicrobial activity against mainly gram-negative and some gram-positive bacteria, and minimal activity against anaerobic bacteria.1 Enrofloxacin might also be effective against organisms in the genera Chlamydia, Mycoplasma (Haemobartonella), Mycobacterium, and Toxoplasma.1,2 The drug (enrofloxacin and its active metabolite ciprofloxacin) is primarily excreted through the kidneys and, depending on the species, can also be metabolized by the liver.1 In various taxa, enrofloxacin is an attractive antimicrobial treatment option because its MIC for susceptible bacteria is usually low and because it has low protein-binding activity, high bioavailability, an extended half-life, and good penetration to multiple body tissues.1
The black-tailed prairie dog (Cynomys ludovicianus) is a herbivorous, burrowing animal in the order Rodentia and the family Sciuridae.3 It is a keystone species in the grasslands of North America and is kept in zoological collections and also as privately owned pets.3–5 Because of a propensity to develop several biliary diseases, these animals are used in gallstone research.6 This species is also used as an animal model for diseases caused by Clostridium difficile, Yersinia pestis, and Francisella tularensis in humans.5 Given that prairie dogs are hindgut fermenters and at risk for digestive dysbiosis, they are suggested to be sensitive to narrow-spectrum antimicrobials that target gram-positive flora.7 Experimentally, prairie dogs given a single IM dose of 100 mg of cefoxitin have developed C difficile cecitis and diarrhea.8 To our knowledge, no antibacterial pharmacokinetic data have been reported for black-tailed prairie dogs to date.
The objective of the study reported here was to investigate the pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin after administration to black-tailed prairie dogs as a single SC injection. Our study hypotheses were that a dose of 20 mg of enrofloxacin/kg SC would result in plasma concentrations within an anticipated therapeutic range and that enrofloxacin would not be further metabolized into ciprofloxacin.
The authors thank Certara for provision of an academic license for use of the Phoenix 64 software and Matt Warner, Christine Hackworth, Brandi Heckel, Sarah Ostrom, Valerie Head, Danielle Fuller, Kirk Nemechek, and Jessie Roberts for technical assistance.
Area under the concentration-versus-time curve from 0 to 24 hours
Percentage of the area under the concentration-versus-time curve extrapolated to infinity
Area under the concentration-versus-time curve extrapolated to infinity
Clearance per fraction of the dose absorbed
Observed maximum plasma concentration
Plasma terminal rate constant
Minimum inhibitory concentration
Time to reach maximum plasma concentration
Mazuri Rodent Breeder 6F, Mazuri Exotic Pet Food, Richmond, Ind.
Baytril, 22.7 mg/mL, Bayer Co, Shawnee Mission, Kan.
Acquity UPLC, Waters Corp, Milford, Mass.
TQD, Waters Corp, Milford, Mass.
Waters CSH, Waters Corp, Milford, Mass
Ostro Pass-through Sample Preparation Plate, Waters Corp, Milford, Mass.
Phoenix 64, Winnonlin, version 7.0, Certara LP, Princeton, NJ.
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