Pharmacokinetics of tetracycline in chickens after intravenous administration

Plasma levels of tetracycline in chickens were determined after intravenous (iv) administration of a 65-mg/kg dose. The disposition kinetics of tetracycline in chickens were fitted to a two-compartment open model. Pharmacokinetic parameters were found to be: A (microgram/ml) = 2000 +/- 450, alpha (hr-1) = 4.3 +/- .5, B (microgram/ml) = 82 +/- 6, beta (hr-1) = .252 +/- .009, K12 (hr-1) = 1.515, K21 (hr-1) = .049, and K10 (hr-1) = 2.652. Biliary excretion of tetracycline was also studied in chickens fitted with cannulae inserted into both bile ducts. The maximum values for tetracycline biliary excretion rate (407 and 606 micrograms/hr) were reached at about 1 hr after iv administration of 10- and 15-mg/kg doses. First-order rate constants for the biliary excretion, Kbi (hr-1), were .834 and .665, respectively. The cumulative biliary excretion study showed that about 7% of both administered doses was recovered from the bile within the first 6 hr. In contrast, there was a low recovery of antibiotic in the bile after oral administration of 100 and 200 mg/kg doses.