A plant alkaloid that inhibits the topoisomerase I enzyme. This enzyme plays a critical role in DNA replication and transcription. Irinotecan is the second most recently approved topoisomerase inhibitor that has become available; the first one is topotecan.

Metastatic carcinoma of the colon or rectum that has progressed or recurred after treatment with 5-fluorouracil. Phase II trials are underway using this drug in ovarian cancer.

Converted to its active metabolites in the liver; excreted through the biliary and renal system. Half-life: 6 hours.

♦ Adult: 125 mg/m² given weekly by IV infusion for 4 weeks, followed by 2 weeks of rest before repeat cycles are given.

♦ Pediatric: Safety and efficacy not studied.

Dilute, preferably with 5% dextrose injection or 0.9% sodium chloride injection, to yield a final concentration of 0.12 to 1.1 mg/mL. The solution is usually infused in 500 mL
5% dextrose in water. The reconstituted solution is stable for up to 24 hours at room temperature (25°C) and in ambient fluorescent lighting. If refrigerated at approximately 2° to 8°C, the drug when diluted with 5% dextrose injection is stable for 48 hours, protected from sunlight. Admixtures with 0.9% sodium chloride should not be refrigerated because of the possibility of particulates. Do not freeze irinotecan or its admixtures because of precipitation.