<；P>；PROBLEM TO BE SOLVED: To provide a new medicine for releasing drug resistance which is a medicine useful for infectious diseases etc., and suitable as a releasing agent for drug resistance in drug resistant diseases. <；P>；SOLUTION: The medicine for releasing the resistance in the drug resistant diseases comprises an opioid receptor ligand as an active ingredient. An opioid &delta； receptor antagonist is preferred as the opioid receptor ligand. The opioid receptor ligand is suitably administered together with a chemotherapeutic agent and used for therapy. Malaria is preferably taken as the object as a causative foreign microorganism of diseases acquiring the resistance to the chemotherapeutic agent from aspects of importance of planning countermeasures for the resistance. <；P>；COPYRIGHT: (C)2008,JPO&INPIT
