Pharmacokinetics and bioavailability of doxycycline in fasted and nonfasted broiler chickens

The pharmacokinetics and the influence of food on the kinetic profile and b ioavailability of doxycycline was studied after a single intravenous (i.v.) and oral dose of 10.0 mg/kg body weight in 7-week-old broiler chickens. Fo llowing i.v. administration the drug was rapidly distributed in the body wi th a distribution half-life of 0.21 +/- 0.01 h. The elimination half-life o f 6.78 +/- 0.06 h was relatively long and resulted from both a low total bo dy clearance of 0.139 +/- 0.007 L/h kg and a large volume of distribution o f 1.36 +/- 0.06 L/kg. After oral administration to fasted chickens, the abs orption of doxycycline was quite fast and substantial as shown by the absor ption half-life of 0.39 +/- 0.03 h, the maximal plasma concentration of 4.4 7 +/- 0.16 mug/mL and the time to reach the C-max of 1.73 +/- 0.06 h. The d istribution and the final elimination of the drug were slower than after i. v. administration. The absolute bioavailability was 73.4 +/- 2.5%. The pres ence of food in the intestinal tract reduced and extended the absorption (t (1/2a) = 1.23 +/- 0.21 h; C-max = 3.07 +/- 0.23 mug/mL; t(max) = 3.34 +/- 0 .21 h). The absolute bioavailability was reduced to 61.1% +/- 4.4%.