Disposition and milk levels of Sulfadiazine-Trimethoprim combination following intrauterine bolus administration in lactating cows during postpartum

This study was carried out to describe the disposition and milk levels of sulfadiazine (SDZ)-trimethoprim (TMP) combination following intrauterine bolus administration in cows during postpartum. Six cows were used as materials. SDZ-TMP combination bolus was given through intrauterine administration at the recommended dose of 4 g of SDZ plus 0.8 g of TMP to each animal during postpartum. Concentrations of SDZ and TMP were determined by HPLC. The absorption half-lives of SDZ and TMP were 1.44 and 1.68 hours, respectively. The elimination half-life of SDZ was 3.74 hours, while it was 11.04 hours for TMP. SDZ did not reach to MIC levels in plasma and milk after the intrauterine administration. After intrauterine administration, TMP was detected at the effective levels in milk. These results suggest that passing ratio of antimicrobials into milk should be taken into consideration for drug administrations into uterine in lactating cows during postpartum.