Oxytetracycline concentrations in plasma and lung of healthy and pneumonic calves, using two oxytetracycline preparations.

Drug concentrations in lung tissue and plasma pharmacokinetics of a long-acting preparation of oxytetracycline were compared with those of a standard preparation of oxytetracycline given to healthy and pneumonic calves. Both preparations achieved higher concentrations in the pneumonic lung when compared with those in the normal-appearing lung of the same group. A difference in concentrations in lung tissue was not found between preparations at either 24 or 48 hours. The plasma pharmacokinetic values did differ between preparations. Comparatively, the long-acting oxytetracycline had a smaller rate constant for disposition, a larger volume of distribution divided by bioavailability constant, and a longer half-life. A difference in pharmacokinetic values was not observed between healthy and pneumonic calves.