Novel chemical conjugates of a psychotropic drug residue and an amino-containing organic acid residue selected to reduce side effects induced by the psychotropic drug when administered per se, to enhance the therapeutic activity of the psychotropic drug and/or to exert anti-proliferative activity, in which the amino group is in the form of an acid addition salt thereof and which are characterized by high stability are disclosed. Further disclosed are processes for preparing the chemical conjugates and addition salts thereof, pharmaceutical compositions containing the chemical conjugates and methods utilizing the chemical conjugates for treating various medical conditions.