Disclosed is a process for manufacturing amorphous rifaximin comprising a) reacting Rifamycin S with 2-amino-4-picoline in presence of suitable solvent b) adding iodine dissolved in suitable solvent to the above reaction mass followed by reducing agent c) adjusting the pH of the reaction mass between 1.5 - 2.5 under stirring d) extracting with water immiscible organic solvent and concentrating the organic layer to form a residue e) stripping the residue obtained in step d) with a water immiscible solvent or mixture of water immiscible solvents to residue. f) stirring the residue obtained in step e) with a water immiscible solvent or mixtures thereof to get a solid g) Filtering the solid and washing with the same solvent/s and h) drying the solid at a temperature below 40 degrees C.
