PROCESSES FOR THE PRODUCTION OF POLYMORPHIC FORMS OF RIFAXIMIN

Crystalline polymorphous forms of rifaximin (INN) antibiotic named rifaximin alpha and rifaximin beta, and a poorly crystalline form named rifaximin gamma, useful in the production of medicinal preparations containing rifaximin for oral and topical use and obtained by means of a crystallization carried out by hot-dissolving the raw rifaximin in ethyl alcohol and by causing the crystallization of the product by addition of water at a determinate temperature and for a determinate period of time, followed by a drying carried out under controlled conditions until reaching a settled water content in the end product, are the object of the invention.