Cefazolin Sodium Imp. K (EP): (6R, 7R)-3-[[(5-methyl-1,3,4-thiadiazol-2-yl)sulfanyl]methyl]-8-oxo-7-[(1H-tetrazol-1-ylacetyl)amino]-5-thia-1-azabicyclo[4.4.0]oct-2-ene-2-carboxamide (Cefazolinamide).