[Pharmacokinetics of 1-phthalidyl-5-fluorouracil (PH-FU)]

The blood level of PH-FU following oral administration to rabbits and tumor-bearing mice was considerably lower than that of Tegafur, HCFU or 5'DFUR, and decreased more rapidly. The t1/2 beta was 0.48 h (rabbits) and 1.74-1.91 h (mice). The blood level of 5-FU derived from PH-FU was higher at an earlier time after administration than that derived from other 5-FU derivatives, but it disappeared more rapidly. The tissue level of PH-FU in S-180-and Lewis lung carcinoma-bearing mice was detected at a low level in various tissues of mice, except for a higher level in the digestive tract and a lower level in the brain and muscle. The tissue level of 5-FU in both types of mice was high in the digestive tract and kidney. The 5-FU level in the 2 kinds of tumor tissues was relatively high and persisted for several hours. After incubating PH-FU and tissue homogenates from humans and mice at 37 degrees C for 2 h, PH-FU was converted to 5-FU very strongly in the liver and kidney, and considerably strongly in the muscle, heart, tongue and testis. In conclusion, PH-FU seems to be characterized by a low blood and tissue level of unchanged drug, a high production of 5-FU and a short duration of the level.