S Giguère1, R W Sweeney, M Bélanger. 1. New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348, USA.
Abstract
OBJECTIVE: To investigate the pharmacokinetics of enrofloxacin in adult horses. DESIGN: 2-dose oral and i.v. cross-over trial followed by multiple oral doses. ANIMALS: 8 clinically normal adult horses. PROCEDURE: Enrofloxacin was administered at dosages of 2.5 mg/kg of body weight to 4 horses and 5.0 mg/kg to 4 other horses. Each dose was given by the intragastric and i.v. routes, using a cross-over design. After the first intragastric dose, 5 additional doses were administered at 12-hour intervals. Enrofloxacin concentrations were measured in serum, synovial fluid, peritoneal fluid, urine, CSF, and endometrial tissues. RESULTS: Disposition of enrofloxacin after i.v. administration conformed to a 2-compartment model with an elimination half-life of 5.95 and 6.09 hours for the low and high dose, respectively. After the first intragastric administration, time to peak concentration was 1.0 +/- 0.35 and 1.25 +/- 0.43 hours, and the bioavailability was 57.39 +/- 8/45 and 62.52 +/- 19.65% for the low and high dose, respectively. After multiple intragastric administration, peak serum concentration (at 72 to 96 hours) was 2.62 +/- 0.61 micrograms/ml for the low dose and 5.97 +/- 1.56 micrograms/ml for the high dose. After multiple intragastric doses, synovial fluid, urine, and endometrial tissue concentrations exceeded serum concentrations. Peritoneal fluid and CSF concentrations were lower than serum concentrations. CONCLUSIONS: Computer modeling of the pharmacokinetic variables suggested that a single daily i.v. administered dose of 5.5 mg/kg, or orally administered doses of 7.5 mg/kg every 24 hours or 4.0 mg/kg every 12 hours, would be effective in horses. Additional studies are necessary to confirm the efficacy and safety of these dosages in a clinical setting.
OBJECTIVE: To investigate the pharmacokinetics of enrofloxacin in adult horses. DESIGN: 2-dose oral and i.v. cross-over trial followed by multiple oral doses. ANIMALS: 8 clinically normal adult horses. PROCEDURE: Enrofloxacin was administered at dosages of 2.5 mg/kg of body weight to 4 horses and 5.0 mg/kg to 4 other horses. Each dose was given by the intragastric and i.v. routes, using a cross-over design. After the first intragastric dose, 5 additional doses were administered at 12-hour intervals. Enrofloxacin concentrations were measured in serum, synovial fluid, peritoneal fluid, urine, CSF, and endometrial tissues. RESULTS: Disposition of enrofloxacin after i.v. administration conformed to a 2-compartment model with an elimination half-life of 5.95 and 6.09 hours for the low and high dose, respectively. After the first intragastric administration, time to peak concentration was 1.0 +/- 0.35 and 1.25 +/- 0.43 hours, and the bioavailability was 57.39 +/- 8/45 and 62.52 +/- 19.65% for the low and high dose, respectively. After multiple intragastric administration, peak serum concentration (at 72 to 96 hours) was 2.62 +/- 0.61 micrograms/ml for the low dose and 5.97 +/- 1.56 micrograms/ml for the high dose. After multiple intragastric doses, synovial fluid, urine, and endometrial tissue concentrations exceeded serum concentrations. Peritoneal fluid and CSF concentrations were lower than serum concentrations. CONCLUSIONS: Computer modeling of the pharmacokinetic variables suggested that a single daily i.v. administered dose of 5.5 mg/kg, or orally administered doses of 7.5 mg/kg every 24 hours or 4.0 mg/kg every 12 hours, would be effective in horses. Additional studies are necessary to confirm the efficacy and safety of these dosages in a clinical setting.