Abstract: Florfenicol,a new type of veterinary chloramphenicols with broad spectrum,has been widely applied in the prevention and control of bacterial diseases in livestock,poultry and aquatic animals.However,it is inconvenience to use due to low aqueous solubility,low concentration of preparations and unstable for long-term storage.In this study,the effects of supplement of dimethyl sulfoxide（DMSO）,methanol and ethanol as a florfenicol cosolvent at a dose of less than 70% on the maximum concentration and the stability of the florfenicol aqueous solution were studied under water temperature of 4℃,20℃ and 30℃.Meanwhile,the antimicrobial effects of the cosolvents were determined by a bacteriostat experiment.The results showed that DMSO was found to be the optimal cocosolvent for the florfenicol aqueous solution and to have the minimum effect on drug potency.As high as 2% florfenicol solution was observed when the methanol was as the cosolvent while only 0.7% florfenicol solution was obtained when the ethanol was as the cosolvent.However,the preparations of florfenicol aqueous solution containing cosolvents methanol and ethanol showed better stability under the lower temperature and long-term storage（7 days） than DMSO did,even though both the methanol and the methanol showed high effect on the bacteriostasis of florfenicol.

Key words: florfenicol, dimethyl sulfoxide(DMSO), methanol, ethanol, solubilizing effects