Use of polymorphic forms of rifaximin for medical preparations

A method for increasing the bioavailability of a rifaximin composition comprising administering a polymorph of rifaximin in Form α, β or γ, wherein said polymorph of rifaximin in Form α has an x-ray powder diffraction pattern comprising peaks at about 7.4, 11.8 and 19.7 degrees 2-θ;

• or at about 6.6, 11.8, and 17.6 degrees 2-θ;
• or at about 7.4, 8.8, and 19.7 degrees 2-θ;
• or at about 7.9, 10.5 and 19.7 degrees 2-θ;
• or at about 6.6, 11.8 and 21.4 degrees 2-θ;
• or at about 7.9, 11.8 and 22.1 degrees 2-θ;
• or at about 6.6, 7.4, 7.9, 8.8, 10.5, 11.8, 17.6, 18.5, 19.7, 21 and 22.1 degrees 2-θ;
• a water content from about 0 to about 3.0% and wherein after administration to a patient in need of such treatment, bioavailable plasma concentration of the rifaximin in Form α reaches a maximum value (Cmax) from about 0.0 ng/ml to about 5.5 ng/ml;
• wherein said rifaximin in Form β comprises x-ray powder diffraction pattern peak positions at about 5.4, 9.0, and 13.1 degrees 2-θ;
• or at about 6.4, 10.4 and 18.3 degrees 2-θ;
• or at about 7.8, 17.1 and 20.9 degrees 2-θ;
• or at about 7.8, 17.1 and 20.9 degrees 2-θ;
• at about 5.4, 7.8, 14.4 and 18.3 degrees 2-θ;
• or at about 5.4, 18.3, 20.9;
• or at about 5.4, 6.4, 7.0, 7.8, 9, 10.4, 13.1, 14.4, 17.1, 17.9, 18.3, and 20.9 degrees 2-θ;
• a water content from about 4.5 to about 100.0% and wherein after administration to a patient in need of such treatment, bioavailable plasma concentration of the rifaximin reaches a maximum value (Cmax) between about 0.0 and about 3.7 ng/ml;
• and wherein said rifaximin in Form γ comprises an x-ray powder diffraction pattern peak position at about 5.0°±0.2°;
• 7.1°±0.2°;
• 8.4°±0.2° degrees 2-θ, a water content from about 0% to about 2% and wherein after administration to a patient in need of such treatment, bioavailable plasma concentration of the rifaximin reaches a maximum value (Cmax) from about 0.0 to about 5000 ng/ml.