Abstract:

【Objective】 Depletion of enrofloxacin and its metabolite in the milk were studied in mastitis cows after a single intramammary dose of 500 mg per quarter. 【Method】 Concentration of enrofloxacin and its metabolite ciprofloxacin were determined by high-performance liquid chromatography with fluorescence detector and the concentration-time data were analyzed by statistical moment principle. 【Result】 Enrofloxacin and its metabolite ciprofloxacin were all at the peak after 2 hours in the administered quarter. The concentrations were (13.16±3.10) μg?ml-1 and (2.79±0.94) μg?ml-1, respectively. Enrofloxacin and its metabolite ciprofloxacin can not be detected after 12 hours and 24 hours. In the healthy quarter enrofloxacin was at the peak after 1 hour and the concentration was (0.19±0.02) μg?ml-1. Enrofloxacin can not be detected after 6 hours. Ciprofloxacin was at the peak after 4 hours and the concentration was (0.51±0.07) μg?ml-1. Ciprofloxacin can not be detected after 24 hours. In the administered quarter, ciprofloxacin showed longer t1/2β which is (1.67±0.20) h in milk and maintained longer period than enrofloxacin. Under the experiment condition, it is suggested that the clinical withdrawal time should not be less than three days. 【Conclusion】 The results showed that enrofloxacin in mastitis cows is of rapid absorption, metabolism and elimination . Enrofloxacin and its metabolite ciprofloxacin are not residuary in milk.

Key words: enrofloxacin, metabolite, depletion, cows, mastitis