Polymorphic forms of rifaximin, processes for their production and uses thereof

The present invention relates to rifaximin polymorphic forms a, b and g, the processes for their prepn. and the use thereof in the manuf. of medicinal prepns. for the oral or topical route. A hydroalcoholic suspension of 5 g of rifaximin g was heated at 40 Deg for 24 h, the suspension was then filtered and the solid was washed with water, then dried under vacuum at room temp. until const. wt. 4 g of rifaximin was obtained, showing a powder X-ray diffractogram corresponding to that of the polymorphic form a and a water content equal to 2.6%.