ceftiofur ceftiofur ceftiofur is an antibiotic of the cephalosporin type (third generation), licensed for use in veterinary medicine. it was first described in 1987. it is marketed by pharmaceutical company zoetis as excenel, naxcel, and excede and is also the active ingredient in that company's spectramast lc (lactating cow formulation) and spectramast dc (dry cow formulation) product. ceftiofurclinical datatrade namesnaxcelahfs/drugs.cominternational drug namesatcvet codeqj01dd90 (who) qj51dd90 (who)legal statuslegal status eu: rx-only identifiers iupac name (6r,7r)-7-amino]-3-(furan-2- carbonylsulfanylmethyl)-8-oxo-5-thia-1- azabicyclooct-2-ene-2-carboxylic acid cas number80370-57-6 ypubchem cid6328657chemspider4886668 yunii83jl932i1ckeggd07657 ychemblchembl222913 ycomptox dashboard (epa)dtxsid7046702 chemical and physical dataformulac19h17n5o7s3molar mass523.55 g·mol−13d model (jsmol)interactive image smiles o=c2n1/c(=c(\cs12nc(=o)c(=n\oc)/c3nc(sc3)n)csc(=o)c4occc4)c(=o)o inchi inchi=1s/c19h17n5o7s3/c1-30-23-11(9-7-34-19(20)21-9)14(25)22-12-15(26)24-13(17(27)28)8(5-32-16(12)24)6-33-18(29)10-3-2-4-31-10/h2-4,7,12,16h,5-6h2,1h3,(h2,20,21)(h,22,25)(h,27,28)/b23-11-/t12-,16-/m1/s1 ykey:zbhxiwjrifevqy-ihmpyvirsa-n y (verify) it is resistant to the antibiotic resistance enzyme beta-lactamase, and has activity against both gram-positive and gram-negative bacteria. e. coli strains resistant to ceftiofur have been reported. the metabolite desfuroylceftiofur also has antibiotic activity. the two compounds are measured together to measure for antibiotic activity in milk (alongside other antibiotics).