Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes. Academic Article uri icon


  • 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 500mg/head daily, divided into two equal doses given at 12-h intervals for 8days. 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 192h, as well as 4, 8, 12, 24, and 36h 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 20.0ng/mL (80mg dose) and 101ng/mL (500mg dose). Mean apparent elimination half-life was 18h (80mg dose) and 20h (500mg 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.

published proceedings

  • J Vet Pharmacol Ther

author list (cited authors)

  • Washburn, K., Fajt, V. R., Plummer, P., Coetzee, J. F., Wulf, L. W., & Washburn, S.

citation count

  • 8

complete list of authors

  • Washburn, K||Fajt, VR||Plummer, P||Coetzee, JF||Wulf, LW||Washburn, S

publication date

  • December 2014