Pharmacokinetics of long acting oxytetracycline in the laboratory rat

Pharmacokinetic parameters of a slow release form of oxytetracycline were determined in the rat. Triexponential pharmacokinetics were displayed after intravenous administration. The half-life of the distribution phase was 0.097 hours, the rapid elimination half-life was 3.74 hours and the slow elimination half-life was 27.26 hours. Subcutaneous and intramuscular injection resulted in a rapid elimination half-life of 6.09 and 6.02 hours, respectively. In comparison, a standard form of oxytetracycline given subcutaneously had a rapid elimination half-life of 4.22 hours. The slow release form of oxytetracycline has a half-life in the rat long enough to maintain serum levels greater than the minimum inhibitory concentration of Mycoplasma pulmonis with a dose interval of 72 hours.