Zag. Vet J. (ISSN. 1110-1458) Vol 29, No. 2, (2001)pp. 1-10 Blood And Tissue Residues Of Doxycycline In Broilers ABO-ZAHRA, A.A., "AMANY, M.SALEM AND "EL-GENDI, A.A.M Dept. of Pharmacology, Fac. of Vet. Med., Kafr-El-Shiekh, Tanta Univ. *Dept. of Meat Hygiene, Fac. of Vet. Med., Moshtohor, Zagazic Univ. "Dept. of Phartnacology, Fac. of Vet. Med., Beni-Suef, Cairo Univ. ABSTRACT Following a single intravenous injection of 20 mg doxycycline/kg b.wt. to normal chickens, the drug obeyed a two compartmsnts open model, with half-life of distribution of 0.27 hour. The elimination half-life following intravenous injection was 4.33 hours. Following a single oral administration of 20 mg/kg b.wt. to normal chicker s, the serum drug concentrations peaked 2 hours post-injection with half-life of absorption equal to 0.42 hou:s. Doxycycline residues in most tissues persisted for 3 days except in liver and kidney which persisted for 5 days after the last oral administration. In conclusion, doxycycline has useful a pharmacokinetic characteristics for effective treatment of infections in poultry. It has been found to be absorbed after oral administration and a therapeutic concentration is achieved .n blood. When the: drug was level orally in a dose of 20 mg/kg for five successive days, a withdrawal time of 5 days might be adequate to predict thai: the concentrations in edible tissues are below accepted drug tolerance levels.