Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes
Article first published online: 30 JUL 2014
© 2014 John Wiley & Sons Ltd
Journal of Veterinary Pharmacology and Therapeutics
Volume 37, Issue 6, pages 607–610, December 2014
How to Cite
Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes. J. vet. Pharmacol. Therap. 37, 607–610., , , , ,
- Issue published online: 14 NOV 2014
- Article first published online: 30 JUL 2014
- Manuscript Accepted: 25 MAY 2014
- Manuscript Received: 5 MAR 2014
- Department of Veterinary Physiology and Pharmacology, Texas A&M University, College of Veterinary Medicine
- NIH. Grant Number: AA18166-2
The objectives of this study were to determine plasma concentrations and pharmacokinetic parameters of feed-grade chlortetracycline (CTC) in sheep after oral administration of 80 or 500 mg/head daily, divided into two equal doses given at 12-h intervals for 8 days. These are the approved, and commonly used but unapproved, feed additive doses, respectively, in the United States for the prevention of ovine infectious abortion.
Blood samples were collected just prior to dosing at 0, 12, 24, 72, 96, and 192 h, as well as 4, 8, 12, 24, and 36 h after the last dose, and noncompartmental pharmacokinetic analysis was performed to estimate elimination half-life and area under the plasma concentration–time curve (AUC).
Mean observed maximum CTC concentrations (Cmax) were 20.0 ng/mL (80 mg dose) and 101 ng/mL (500 mg dose). Mean apparent elimination half-life was 18 h (80 mg dose) and 20 h (500 mg dose).
Although published data do not exist to estimate plasma CTC concentrations necessary for the prevention of ovine infectious abortion, concentrations reached in our study suggest that either the FDA-approved and FDA-unapproved dosages are not high enough or that the pharmacodynamic parameter relating preventive dose to pathogen minimum inhibitory concentrations is yet to be determined.