The influence of days post partum on chloramphenicol absorption from the bovine uterus

Chloramphenicol at a single dose of 5.5 mg/kg of body weight was administered by intrauterine infusion to 12 normal cows at varying lengths of time ranging from 14 to 90 days post partum. At approximately 45 days following intrauterine infusion of the drug, chloramphenicol was administered intravenously to 10 of the same cows, again at a single dose of 5.5 mg/kg of body weight. Serum concentrations at various time intervals following the two routes of administration were then compared to determine the fraction of chloramphenicol absorbed from the uterus to the systemic circulation. Cows less than or equal to 60 days post partum absorbed an average of 27.4% of the dose from the uterus over a 48 hour period, while those greater than 60 days post partum absorbed 54.6% of the dose. However, this difference was not statistically significant when evaluated using the t-test at the 0.05 level of significance. The half-life (t (1 2 )) of chloramphenicol in serum was only 80 minutes. The data collected indicates extensive distribution of chloramphenicol to the tissues following intrauterine infusion and suggests the need for a two compartment model in describing chloramphenicol pharmacokinetics and for calculation of the fraction reaching the systemic circulation.