Irinotecan Hydrochloride (CPT-11 hydrochloride) is the hydrochloride salt of a semisynthetic derivative of camptothecin. Irinotecan, a prodrug, is converted to a biologically active metabolite 7-ethyl-10-hydroxy-camptothecin (SN-38) by a carboxylesterase-converting enzyme. One thousand-fold more potent than its parent compound irinotecan, SN-38 inhibits topoisomerase I activity by stabilizing the cleavable complex between topoisomerase I and DNA, resulting in DNA breaks that inhibit DNA replication and trigger apoptotic cell death. Because ongoing DNA synthesis is necessary for irinotecan to exert its cytotoxic effects, it is classified as an S-phase-specific agent.

Irinotecan Hydrochloride（100 mg/kg i.p.）注射以后以剂量和时间依赖的方式影响体重变化（P<0.01）。在注射Irinotecan Hydrochloride（CPT-11）后的第 3 天和第 4 天，观察到平均最大体重减轻。注射Irinotecan Hydrochloride（CPT-11）后，17:00 时的平均体重损失最小。此外，在 5:00 或 9:00 时注射Irinotecan Hydrochloride（CPT-11）后，平均体重下降幅度最大[2]。

Irinotecan Hydrochloride（100 mg/kg i.p.）注射以后以剂量和时间依赖的方式影响体重变化（P<0.01）。在注射Irinotecan Hydrochloride（CPT-11）后的第 3 天和第 4 天，观察到平均最大体重减轻。注射Irinotecan Hydrochloride（CPT-11）后，17:00 时的平均体重损失最小。此外，在 5:00 或 9:00 时注射Irinotecan Hydrochloride（CPT-11）后，平均体重下降幅度最大[2]。

Irinotecan hydrochloride is dissolved in DMSO and stored, and then diluted with appropriate medium before use[1]. To determine the effects of Irinotecan in combination with 5-FU, the MTT assay is used. Depending on the cell lines, 10,000 to 20,000 cells per well are seeded in 96-well plates and incubated for 24 h in complete medium. On day 2, cells are incubated in the absence or presence of Irinotecan for 30 min followed by 5-FU for 24 h. After another 24 h in complete medium without any additives, MTT reagent is added on day 4 to initiate the assay and the cells are incubated for an additional 4 h at 37°C. After removal of the medium and dissolving the crystals with acidified isopropanol, the samples are analyzed using an ELISA plate reader at 570 nm. The value at 650 nm is subtracted as background[1].