Method for preparing a rifaximin product

1. A method for preparing a rifaximin product comprising:

(a) dissolving crude rifaximin in heated absolute ethanol;

(b) precipitating the rifaximin by cooling the solution, without the addition of antisolvent;

(c) collecting the solid by filtering and washing; and

(d) drying the solid.

2. The method according to claim 1 , wherein the solution in step (b) is cooled to 8-25° C.

3. The method according to claim 2 , wherein the solution in step (a) is heated to 40-60° C.

4. The method according to claim 3 , wherein the solid in step (d) is dried under vacuum at 60-70° C.

5. The method according to claim 3 , wherein the solid in step (d) is dried until the solid attains a KF value of less than 4%.

6. The method according to claim 5 , wherein the crude rifaximin in step (a) is dissolved in absolute ethanol in the presence of ascorbic acid.

7. The method according to claim 6 , wherein the crude rifaximin has a water content of between 4 and 7%.

8. A method for preparing a rifaximin product comprising:

(a) dissolving crude rifaximin in a heated solvent selected from C 1 to C 4 alcohols;

(b) precipitating the rifaximin by cooling the solution, without the addition of antisolvent;

(c) collecting the solid by filtering and washing; and

(d) drying the solid.

9. The method according to claim 8 , wherein the solution in step (b) is cooled to 8-25° C.

10. The method according to claim 9 , wherein the solution in step (a) is heated to 40-60° C.

11. The method according to claim 10 , wherein the solid in step (d) is dried under vacuum at 60-70° C.

12. The method according to claim 10 , wherein the solid in step (d) is dried until solid attains a KF value of less than 4%.

13. The method according to claim 12 , wherein the crude rifaximin in step (a) is dissolved in absolute ethanol in the presence of ascorbic acid.

14. The method according to claim 13 , wherein the crude rifaximin has a water content of between 4 and 7%.

15. A method for preparing a rifaximin product comprising:

(a) dissolving crude rifaximin in absolute ethanol heated to 40-60° C.;

(b) precipitating the rifaximin by allowing the solution to cool to 18-25° C. and stirring for three hours;

(c) further cooling the solution to 8-12° C. and stirring for two hours;

(d) collecting the solid by filtering and washing; and

(e) drying the solid.

16. The method according to claim 15 , wherein the solid in step (e) is dried under vacuum at 60-70° C.

17. The method according to claim 16 , wherein the solid in step (e) is dried until the solid attained a KF value of less than 4%.

18. The method according to claim 17 , wherein the crude rifaximin has a water content of between 4 and 7%.

19. The method according to claim 18 , wherein the crude rifaximin is dissolved in absolute ethanol in the presence of ascorbic acid.

20. The method according to claim 19 , wherein the crude rifaximin in step (a) is dissolved in approximately 10 milliliters of absolute ethanol per gram of crude rifaximin.