PURPOSE: The titled preparation that contains a quinoxaline derivative as an active ingredient to control the inflow and outflow of the anticancer agent through the cell membrane, thus increasing the anticancer activity.

CONSTITUTION: The objective preparation contains 1-(2-dialkylaminoalkyl)-3-(p- alkoxybenzyl)-1,2-dihydroquinoxalin-2-one or its salt as an active ingredient. Especially, the compound that has ethyls as the two alkyls and methoxy as the alkoxy is most preferred among these quinoxaline compounds. The anticancer agent develops its effect, when it is transferred through the cell membranes into the cells. Further, cancer cells become resistant, mostly because the accumuation and activity of the anticancer agent become low inside the cancer cells, but the quinoxaline derivatives inhibit the anticancer agent from flowing out of the cells to keep the high concentration of the agent inside the cells. Resultingly, the does of the anticancer agent can be reduced and the troubles are overcome in resistance to anticancer agents.