The present invention relates to a method for treating a subject with a cancer resistant to a chemotherapeutic drug comprising administering to said subject a therapeutically effective amount of prochlorperazine or its analog or metabolite, or a pharmaceutically acceptable salt thereof, in combination of the chemotherapeutic drug. The present invention also relates to a method for preventing cancer metastasis with the combination of prochlorperazine in combination of a chemotherapeutic drug.
