Oral Enrofloxacin as a Promising Antibiotic Therapeutic Option for Nondomestic Ruminants
Providing antibiotic therapy to nondomestic ruminants is an ongoing challenge for veterinarians due to handling and administration constraints and lack of pharmacokinetic-pharmacodynamic data. Oral treatment offers the opportunity to reduce the stress and risk of trauma associated with physical restraint or remote drug administration. Enrofloxacin (Baytril®, Bayer Corp., Shawnee, MI) is a synthetic fluoroquinolone antimicrobial. This study evaluated single-dose pharmacokinetic-pharmacodynamic parameters of enrofloxacin for three different routes (IV, SC, and PO) following administration to six alpacas (Lama pacos) (weight range 63–78 kg) and for two routes (IV and PO) following administration to four goral (Nemorrhaedus goral arnouxianus) (weight range 25–35 kg). Using a cross-over design, each animal received a single dose of 10 mg/kg PO, 5 mg/kg IV, and (alpacas only) 5 mg/kg SC. Blood samples from the goral were collected prior to dosing and at 4, 8, 12, and 24 hours post-administration. Samples were collected from the alpacas prior to dosing and at 10 minutes, 20 minutes, 30 minutes, 1, 2, 4, 6, 8, 12, 24, 36, and 48 hours post-administration. Plasma samples were analyzed for enrofloxacin and ciprofloxacin using high-performance liquid chromatography (HPLC) and UV detection. Pharmacokinetics were determined and include the following mean calculations (Cmax and AUC calculations include enrofloxacin and the active metabolite ciprofloxacin):
Terminal half-life (IV, SC, and oral) = 11.2, 8.7, and 16.1 hours, respectively; systemic availability (SC, oral) = 90.17% and 29.31%; peak concentration (Cmax) (SC, oral) = 3.79 and 1.81 µg/ml; area under the curve (AUC) (SC, oral) = 50.05 and 33.97 µg h/ml.
Terminal half-life (IV and oral) = 13 and 5.2 hours, respectively; systemic availability (oral) = 14.6%; Cmax (oral) = 3.33 µg/ml; AUC (oral) = 27 µg hr/ml.
Based on the inherent antibiotic properties of enrofloxacin, the pharmacokinetic values generated for the oral dosing in this study, and the minimum inhibitory concentrations (MIC) of many gram-positive and gram-negative bacterial pathogens common to ruminants, oral administration of enrofloxacin at a dose rate of 10 mg/kg every 24 hours is an appropriate antimicrobial therapy in alpacas and goral. No adverse gastrointestinal effects were noted during the study, following a 10-day 10 mg/kg every 24-hour dose regimen in the alpacas, or over a one-month observational period following the study.