Effects of oral administration of S-1 on the pharmacokinetics of SN-38, irinotecan active metabolite, in patients with advanced colorectal cancer.

Previous studies have assessed the efficacy and safety of combined treatment with irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin, CPT-11) and S-1, containing tegafur, a prodrug of 5-fluorouracil, in the treatment of colorectal and gastric cancer. The objective of this study was to describe the interaction between CPT-11 and S-1 in 4 patients with colorectal cancer. Coadministration of S-1 changed the pharmacokinetic behavior of CPT-11 and its metabolites.