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Pharmacokinetics of acyclovir after single intravenous and oral administration to adult horses.
|Title||Pharmacokinetics of acyclovir after single intravenous and oral administration to adult horses.|
|Publication Type||Journal Article|
|Year of Publication||2006|
|Authors||Bentz BG, Maxwell LK, Erkert RS, Royer CM, Davis MS, MacAllister CG, Clarke CR|
|Journal||Journal of veterinary internal medicine / American College of Veterinary Internal Medicine|
|Date Published||2006 May-Jun|
|Keywords||Acyclovir, Administration, Oral, Animals, Antiviral Agents, Area Under Curve, Chromatography, High Pressure Liquid, Cross-Over Studies, Female, Herpesviridae Infections, Herpesvirus 1, Equid, Horse Diseases, Horses, Injections, Intravenous, Male|
The purpose of the study reported here was to describe the bioavailability and pharmacokinetics of acyclovir after intravenous and oral administration to horses. Six healthy adult horses were used in a randomized cross-over study with a 3 x 3 Latin square design. Three treatments were administered to each horse: 10 mg of injectable acyclovir/kg of body weight in 1 L of normal saline delivered as an infusion over 15 minutes; 10 mg of acyclovir/kg in tablets by nasogastric intubation; and 20 mg of acyclovir/kg in tablets by nasogastric intubation. A 2-week washout period was provided between each treatment. Serum samples were obtained for acyclovir assay using reversed-phase, high-performance liquid chromatography with fluorescence detection. Deproteinated serum was injected onto a C18 column, and elution occurred under isocratic conditions. The limit of quantification was 0.04 microg/mL. The assay exhibited suitable accuracy, precision, and recovery. The IV data were analyzed by a 3-compartment model, and oral data were analyzed noncompartmentally. Intragastric acyclovir administration at either dose was associated with high variability in serum acyclovir-time profiles, low Cmax, and poor bioavailability. The dosage of 20 mg/kg was associated with mean (+/- SD) Cmax of 0.19 +/- 0.10 microg/mL, and bioavailability was 2.8%. Inhibition of equine herpesvirus has been reported to require significantly higher acyclovir concentrations than those obtained here. The results of this study do not support a therapeutic benefit for the oral administration of acyclovir up to doses of 20 mg/kg.
|Alternate Journal||J. Vet. Intern. Med.|