- A drug used alone or with other drugs to treat colorectal cancer that has spread to other parts of the body. It is used in patients whose cancer has not already been treated or whose cancer has recurred (come back) or has gotten worse after treatment with anticancer drugs that included fluorouracil. It is also being studied in the treatment of other types of cancer. Irinotecan hydrochloride blocks a certain enzyme needed for cell division and DNA repair, and it may kill cancer cells. It is a type of topoisomerase inhibitor and a type of camptothecin analog. Irinotecan is the active ingredient of irinotecan hydrochloride. Also called Camptosar and CPT 11.