Abstract

Nile tilapia (Oreochromis niloticus) were medicated with erythromycin base via the medicated ration at 50 and 100 mg erythromycin·kg^-1 fish body weightday^-1 for 7 days. Erythromycin residues in their muscle were determined by LC-MS/MS method through TUV Rheinland Aimex Vietnam Co., Ltd.  The results predicted withdrawal time for Nile tilapia was 33 days (908°C-day) if treated by the former dose or 42 days (1150°C-day) if treated by the later dose under our experimental conditions. Derivative biotransformation of erythromycin such as erythromycin C, E, F appeared in post-dosing stage, all of them were depleted to safe level if we strictly followed the withdrawal time and chemotherapeutic dosage as recommendation.

Key words: Erythromycin, tilapia; withdrawal time, LC-MS/MS, biotransformation.