[Studies on reversing effect of multidrug resistance by dipyridamole. II. Inhibition of epirubicin efflux from resistant cells by dipyridamole and its pharmacological effect].

We have previously reported that dipyridamole increases the cytotoxicity of epirubicin and alters the cell cycle in doxorubicin-resistant (P388/DOX) cells, increasing the accumulation of G2/M phase by blocking the cell cycle. In cultured cells, dipyridamole increased dose-dependently the intracellular accumulation of epirubicin in the resistant cells. Simultaneous exposure of the resistant cells to epirubicin and 100 microM dipyridamole resulted in a 4.