Pharmacokinetics of enrofloxacin administered intravenously and orally to foals.
OBJECTIVE
To determine the pharmacokinetics of enrofloxacin administered IV and orally to foals.


METHODS
5 clinically normal foals.


METHODS
A 2-dose cross-over trial with IV and oral administration was performed. Enrofloxacin was administered once IV (5 mg/kg of body weight) to 1-week-old foals, followed by 1 oral administration (10 mg/kg) after a 7-day washout period. Blood samples were collected for 48 hours after the single dose IV and oral administrations and analyzed for plasma enrofloxacin and ciprofloxacin concentrations by use of high-performance liquid chromatography.


RESULTS
For IV administration, mean +/- SD total area under the curve (AUC0-infinity) was 48.54 +/- 10.46 microg x h/ml, clearance was 103.72 +/- 0.06 ml/kg/h, half-life (t1/2beta) was 17.10 +/- 0.09 hours, and apparent volume of distribution was 2.49 +/- 0.43 L/kg. For oral administration, AUC0-infinity was 58.47 +/- 16.37 microg x h/ml, t1/2beta was 18.39 +/- 0.06 hours, maximum concentration (Cmax) was 2.12 +/- 00.51 microg/ml, time to Cmax was 2.20 +/- 2.17 hours, mean absorption time was 2.09 +/- 0.51 hours, and bioavailability was 42 +/- 0.42%.


CONCLUSIONS
Compared with adult horses given 5 mg of enrofloxacin/kg IV, foals have higher AUC0-infinity, longer t1/2beta, and lower clearance. Concentration of ciprofloxacin was negligible. Using a target Cmax to minimum inhibitory concentration ratio of 1:8 to 1:10, computer modeling suggests that 2.5 to 10 mg of enrofloxacin/kg administered every 24 hours would be effective in foals, depending on minimum inhibitory concentration of the pathogen.
Bermingham
E C
EC
Department of Anatomy, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
Papich
M G
MG
Vivrette
S L
SL
D000284:Administration, Oral; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D002939:Ciprofloxacin / Q000097:blood; D003198:Computer Simulation; D018592:Cross-Over Studies; D000077422:Enrofloxacin; D024841:Fluoroquinolones; D006207:Half-Life; D006736:Horses / Q000378:metabolism*; D007275:Injections, Intravenous / Q000662:veterinary; D015363:Quinolones / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*; D012044:Regression Analysis
D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D015363:Quinolones; D000077422:Enrofloxacin; D002939:Ciprofloxacin