The comparative bio-equivalence of Dolistin and Colidox at a dose rate of 10 mg doxycycline/kg ® ®
b. wt. was studied in 48 clinically normal broiler chickens. After oral administration, plasma levels of doxycyline
peaked after 2 hours post-dosing without significant differences between the two products and it could be
detected therapeutically and exceeded the minimum inhibitory concentration (MIC) for most micro-organisms
sensitive to doxycycline for 12 hours. The disposition kinetics of doxycycline in the two products following
oral administration revealed that the maximum plasma concentration (C .) were 22.65 and 21.80 µg/ml and max
attained at (t .) 2.10 and 2.20 hours, respectively. Doxycycline in both of the products was eliminated with half- max
lives (t ) equal to 7.70 and 6.93 hours, respectively. The mean systemic bioavailabilities of doxycycline in both 0.5â
of the products after oral administration in chickens were 80.60 and 79.70%, respectively. Doxycycline residues
in Dolistin and Colidox after repeated oral administration in chickens were detected in all the tested tissues ® ®
(liver, kidney, lung and muscle). Doxycycline of both of the products was completely cleared from the chicken’s
bodies 6 days after the last oral dose. Colistin in both of the products could not be detected in blood or tissues
after oral administration that makes it the antibiotic of choice for the treatment of enteric infections caused by
organisms sensitive to colistin. It was concluded that doxycycline in the form of Dolistin and Colidox needs ® ®
6 days for withdrawal in chickens and a dose equivalent to 20 mg doxycycline/kg a day is better to keep the
plasma concentration higher than the MIC |
