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 s ulfadiazine (SDZ)-trimethoprim (TMP) combination following intrauterine bol us administration in cows during postpartum. Six cows were used as material s. 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 duri ng postpartum. Concentrations of SDZ and TMP were determined by HPLC. The a bsorption 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 intra uterine 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 adm inistrations into uterine in lactating cows during postpartum.