Calcium Aluminosilicate Anti-Diarrheal in Treating and Preventing Diarrhea in Patients With Metastatic Colorectal Cancer Receiving Irinotecan

DISEASE CHARACTERISTICS: * Diagnosis of colorectal cancer * Metastatic disease * Scheduled to receive irinotecan hydrochloride alone or in combination with fluorouracil, cetuximab, leucovorin calcium, or other biological therapy (including bevacizumab) * No uncontrolled brain metastasis * Previously treated brain metastasis allowed PATIENT CHARACTERISTICS: * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Absolute neutrophil count (ANC) \> 1,000/mm³ * Platelet count \> 100,000/mm³ * Total bilirubin \< 1.5 times upper limit of normal (ULN) * Aspartate aminotransferase (AST or SGOT) and/or alanine aminotransferase (ALT or SGPT) \< 2.5 times ULN (\< 5 times ULN if liver metastasis is present) * Alkaline phosphatase \< 2.5 times ULN * Creatinine clearance \> 35 mL/min * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No known UDP-glucuronosyltransferase 1A1 (UGT1A1) deficiency with homozygotes. * No known history of Gilbert's disease * No diarrhea \> grade 1 * No serious illness or medical condition, including any of the following: * Uncontrolled congestive heart failure * Uncontrolled hypertension (i.e., blood pressure \> 150/100 mm Hg) * Uncontrolled arrhythmia * Active angina pectoris * Symptomatic heart disease according to New York Heart Association(NYHA) class II-IV * No serious uncontrolled active infection * No existing colostomy or ileostomy * Not able to take and document oral study medications * No history of allergies to irinotecan hydrochloride * No history of significant neurological or psychiatric disorders that would preclude giving consent or participating in study treatment or follow up PRIOR CONCURRENT THERAPY: * See Disease Characteristics * Prior treatment for metastatic disease allowed * At least 4 weeks since prior irinotecan * More than 2 weeks since prior chemotherapy * Irinotecan alone or in combination with other chemotherapy or biologic agents allowed * More than 4 weeks since prior radiotherapy * No concurrent radiotherapy * No concurrent medication schedule that does not permit a 2-hour window between administration of calcium aluminosilicate anti-diarrheal (CASAD) and other medications