Pharmacokinetics and bioavailability of doxycycline hyclate after oral administration in calves

The bioavailability and pharmacokinetics of doxycycline hyclate were determined in calves with immature rumen function. The bioavailability of doxycycline after oral administration in a milk replacer was approximately 70%. The elimination half-life of doxycycline was found to be 9.5 +/- 3.0 h. after intravenous administration, and 12.6 +/- 5.0 h. after single oral administration. Plasma concentrations were determined after repeated oral administration of doxycycline dissolved in a milk replacer, at a dose of 5 mg per kg body weight, twice daily. During the period of administration, the plasma concentrations varied between Cmin of 1.0 +/- 0.19 mg/L and Cmax of 2.3 +/- 0.19 mg/L.