Inclusion Criteria:

- signed written informed consent

- histologically proven colorectal cancer patients started new line of chemotherapy
based on irinotecan

- ECOG PS 0 - 1 at study entry

- life expectancy more than 3 months

- absence of any psychological, familial, sociological or geographical condition
potentially hampering compliance with the study protocol and follow-up schedule;

Exclusion Criteria:

- impossibility to take oral medication

- active infection treated by antibiotic therapy

- ileostomy

- hypersensitivity to study drug

- any concurrent malignancy other than non-melanoma skin cancer, no other cancer in
past 5 years.

- serious concomitant systemic disorders or diseases incompatible with the study (at
the discretion of investigator )