Fidaxomicin is a recently marketed antibiotic with a confusing history dating back to its original isolation in 1975. Fidaxomicin is the major analogue of a family of macrocyclic lactones, isolated independently by three different groups from cultures belonging to three different genera (Actinoplanes, Dactylosporangium and Micromonospora) known as lipiarmycin A3, tiacumicin B and clostomicin B1, respectively. Fidaxomicin is a narrow-spectrum antibiotic with excellent activity against Gram-positive bacteria, notably Clostridium difficile. Fidaxomicin acts in the gastrointestinal tract without undue disruption to gut microbial flora.Fidaxomicin is soluble in ethanol, methanol, DMF or DMSO. Limited water solubility.