Egg residue and depletion in Rhode Island Red hens (Gallus gallus domesticus) following multiple oral doses of trimethoprim-sulfamethoxazole.

Sulfamethoxazole-Trimethoprim residues in eggs can cause risks to human health. The most common cause of residues in eggs results from failure to meet an appropriate withdrawal interval. The aim of this study was to determine the quantity and duration of sulfamethoxazole-trimethoprim residues in eggs and evaluate the drug elimination parameters in egg components and whole egg to better estimate the withdrawal interval of sulfamethoxazole and trimethoprim following oral administration for 7 days at a purposed dosage regimen (time average 46 mg kg day for sulfamethoxazole, time average 25 mg kg day for trimethoprim). Residues of sulfamethoxazole and trimethoprim in albumen and yolk were analyzed by ultra-performance liquid chromatography mass spectrometry. A greater percentage of sulfamethoxazole was distributed into the albumen (91.53-96.74%) and a greater percentage of trimethoprim was distributed into yolk (63.92-77.36%) during treatment. The residues levels in whole egg declined below or reached the limit of quantification until 13 days for SMZ and TMP respectively. The withdrawal interval for SMZ and TMP were 43 days and 17 days respectively using the FDA tolerance method.