New polymorphous forms of rifaximin, processes for their production and use thereof in the medicinal preparations.

Cryst. polymorphous forms of the rifaximin (INN) antibiotic named rifaximin  and rifaximin  useful in the prodn. of medicinal prepns. contg. rifaximin for oral and topical use and obtained by means of a crystn. process carried out by hot-dissolving the raw rifaximin in Et alc. and by causing the crystn. of the product by addn. of water at a determinate temp. 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

The structure–property relationship of four crystal forms of rifaximin

none6noThe crystal structures of four crystal forms of rifaximin, named a, b, d and e, have been elucidated by a combination of single crystal and powder diffraction experiments with synchrotron and X-ray sources. The crystal structures of the d and e forms have been determined from powder diffraction data alone. Hot stage microscopy has also been of paramount importance in the understanding of the b -> a conversion process.mixedD. Braga; F. Grepioni; L. Chelazzi; M. Campana; D. Confortini; G. C. ViscomiD. Braga; F. Grepioni; L. Chelazzi; M. Campana; D. Confortini; G. C. Viscom