Intraperitoneal injection of dipyridamole increases the life span of tumor bearing mice treated with fluorouracil.

This study was carried out to investigate the effect of the Fluorouracil (5-FU) and Dipyridamole (DP) combination on the growth of P388 murine lymphoid neoplasms. The first stage was to determine the lethal dose (LD 50) for each compound (5-FU, DP) to normal B6D2F1 mice after intraperitoneal (i.p.) injection. The LD 50 were 700 and 54 mg/kg for DP and 5-FU respectively. B6D2F1 mice bearing P388 ascitic tumors and receiving a 4-day schedule of 5-FU (2 mg/kg/day) with DP (100 mg/kg/day) 1 hr before each 5-FU dose were studied. DP was found to lower significantly (p < 0.0001) the mortality of 5-FU in tumor bearing mice by nearly 2.5 fold. This study aims at defining the best dose combination of intraperitoneal injection of 5-FU in conjunction with DP. These data allow a prospective evaluation of 4-day, i.p. 5-FU and DP with an increase of life span without toxic death.