The pharmacokinetics of chlortetracycline orally administered to turkeys: influence of citric acid and Pasteurella multocida infection.

A physiologically based pharmacokinetic model was developed to describe the absorption and disposition of chlortetracyline (CTC) in the healthy and diseased (fowl cholera) turkey. The CTC was given (with and without citric acid) as an oral (15 mg/kg) or i.v. (1 mg/kg) dose. When minerals (0.3 g/L Ca2+, 0.1 g/L Mg2+) were dissolved in the bird's drinking water, the model indicated that the addition of citric acid (mass ratio of 10 citrate: 1 CTC) increased the fraction of dose absorbed from 0.06 to 0.16; once absorbed, the fractions of drug eliminated by renal excretion, biliary secretion, and chemical decomposition were 50, 46, and 4%, respectively. The presence of fowl cholera appeared to increase plasma levels by increasing the intestinal permeability and lowering the hepatic and/or renal clearance.