... 5-FU at 400 mg/m2/day for days 1-5 and 8-12, infusion of CDDP or NDP at 40 mg/m2/day on days 1 and 8, and radiation at 2 Gy/day on days 1 to 5, 8 to 12, and 15 to 19, with a second course ... were determined by high performance liquid chromatogra-phy at 5 PM on days 3, 10, 38 and4 5, and at 5 AM on days 4, 11, 39 and 46. Results and conclusions: The circadian rhythm in plasma concentrations ... on days 3, 10, 38 and 45, and at 5 AM on days 4, 11, 39 and 46 [11-13]. The plasma concentration of 5-FU was determined by high-performance liquid chromatog-raphy as described previously [11-13]....