Depletion of trimethoprim and sulphadiazine from eggs of laying hens receiving trimethoprim/sulphadiazine combination

The depletion of trimethoprim (TRM) and sulphadiazine (SDZ) in egg yolk and egg albumen of laying hens was studied after administration of TRM/SDZ combination in a dose of 0.2 and 0.4 g l−1 drinking water for five successive days. TRM and SDZ were extracted using a solid-phase extraction method and assayed by HPLC. TRM and SDZ appeared in egg yolk and egg albumen 1 day after administration of 0.2 or 0.4 g l−1 drinking water. Maximum concentration of TRM and SDZ was achieved 1 day after drug withholding. Maximum concentration of TRM was 0.43 and 0.81 μg g−1 in egg yolk and 0.24 and 0.43 μg g−1 in egg albumen after a dose of 0.2 and 0.4 g l−1 drinking water, respectively. Maximum concentration of SDZ was 0.15 and 0.18 μg g−1 in yolk and 0.22 and 0.32 μg g−1 in albumen after administration of the small and the large dose, respectively. TRM was detected up to day 5 and 7 in egg yolk and day 4 and 6 in albumen following the small and large dose, respectively. SDZ was detected up to day 4 and 6 in egg yolk and day 5 and 7 in egg albumen after the small and large dose, respectively. A suggested withdrawal time to tolerance level (0.05 and 0.1 μg g−1 for TRM and SDZ, respectively) is not less than 3 and 4 days after the use of 0.2 and 0.4 g l−1 drinking water, respectively