Rifampicin test as a predictor of Irinotecan toxicity in metastatic colorectal cancer.

Interventions: The patients with metastatic colorectal cancer being considered for Irinotecan treatment will take single 900 mg dose of oral rifampicin. Bilirubin levels will be measured after 4 hours. The patients will go on to have standard Irinotecan treatment. There will be at least 48 hours interval between rifampicin ingestion and irinotecan treatment. They will be monitored for toxicities especially diarrhoea and neutropenia after cycle 1 irinotecan. A correlation will be done between rise in bilirubin and toxicities. Both the intervention- rifampicin intake and irinotecan administration will be on a single day only 2 days apart. Patients will be monitored for 3 weeks after irinotecan dose for toxicities. Blood will also be analysed for UGT 1A1 polymorphism and correlated with toxicities and rise in bilirubin.
Primary outcome(s): To determine if rifampicin induced hyperbilirubinemia can predict irinotecan toxicity.[Measured on day 21 after irinotecan dose.]
Study Design: Purpose: Diagnosis; Allocation: Non-randomised trial; Masking: Open (masking not used);Assignment: Single group;Type of endpoint: Safety