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Abstract

Objective

To investigate the pharmacokinetics of enrofloxacin in adult horses.

Design

2-dose oral and IV 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 IV 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 IV 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 bioavailabihty 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 μg/ml for the low dose and 5.97 ± 1.56 μg/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 IV 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. (Am J Vet Res 1996;57:1025–1030)

Free access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine pharmacokinetics and pulmonary disposition of minocycline in horses after IV and intragastric administration.

ANIMALS 7 healthy adult horses.

PROCEDURES For experiment 1 of the study, minocycline was administered IV (2.2 mg/kg) or intragastrically (4 mg/kg) to 6 horses by use of a randomized crossover design. Plasma samples were obtained before and 16 times within 36 hours after minocycline administration. Bronchoalveolar lavage (BAL) was performed 4 times within 24 hours after minocycline administration for collection of pulmonary epithelial lining fluid (PELF) and BAL cells. For experiment 2, minocycline was administered intragastrically (4 mg/kg, q 12 h, for 5 doses) to 6 horses. Plasma samples were obtained before and 20 times within 96 hours after minocycline administration. A BAL was performed 6 times within 72 hours after minocycline administration for collection of PELF samples and BAL cells.

RESULTS Mean bioavailability of minocycline was 48% (range, 35% to 75%). At steady state, mean ± SD maximum concentration (Cmax) of minocycline in plasma was 2.3 ± 1.3 μg/mL, and terminal half-life was 11.8 ± 0.5 hours. Median time to Cmax (Tmax) was 1.3 hours (interquartile range [IQR], 1.0 to 1.5 hours). The Cmax and Tmax of minocycline in the PELF were 10.5 ± 12.8 μg/mL and 9.0 hours (IQR, 5.5 to 12.0 hours), respectively. The Cmax and Tmax for BAL cells were 0.24 ± 0.1 μg/mL and 6.0 hours (IQR, 0 to 6.0 hours), respectively.

CONCLUSIONS AND CLINICAL RELEVANCE Minocycline was distributed into the PELF and BAL cells of adult horses.

Full access
in American Journal of Veterinary Research