[The antitumor activity of intraperitoneally- or orally-administered etoposide in animals and its...

The antitumor activity of etoposide against a wide variety of transplantable tumors in mice and rats was examined. Etoposide exhibited antitumor activity by both i.p. and p.o. administrations but a much larger effect was obtained in the former case. In addition, the effective dose of etoposide was much less in i.p. administration. In order to further investigate this large difference of etoposide effect the level of etoposide in the blood was followed after administration of 3H-etoposide via i.p. and p.o. routes. Although the maximum levels for both were seen 10 to 20 min after administration, the level in i.p. administration was much higher than that in p.o. administration. For instance, the level seen for i.p. administration at 8 mg/kg was comparable to that for p.o. administration at a much higher dose of 128 mg/kg. The administration schedule dependency of etoposide antitumor activity was examined using L1210 leukemia as the target tumor. When etoposide was administered alone on day, 1, the effect was the smallest obtained in i.p. as well as in p.o. administrations among the schedules examined in this study. Under other schedules where etoposide was administered i.p. and p.o. once a day for 3, 5 and 9 consecutive days from day 1 and on every other day, that is, days 1, 3 and 5, higher antitumor effects were seen.