* Clozapine is generally considered to be more effective than other antipsychotic drugs. Clozapine is often used in treatment-resistant schizophrenia (poor treatment response to 2 or more antipsychotic drugs). So a switch from clozapine to another antipsychotic drug could cause problems regarding effectiveness.<ref> McEvoy J P etal. al, [http://ajp.psychiatryonline.org/cgi/content/full/163/4/600 Effectiveness of clozapine versus olanzapine, quetiapine, and risperidone in patients with chronic schizophrenia who did not respond to prior atypical antipsychotic treatment]. Am J Psychiatry. 2006;163:600–610.</ref> <ref> Lewis S W et al., [http://schizophreniabulletin.oxfordjournals.org/cgi/content/abstract/32/4/715 Randomized Controlled Trial of Effect of Prescription of Clozapine Versus Other Second-Generation Antipsychotic Drugs in Resistant Schizophrenia]. Schizophrenia Bulletin vol. 32 no. 4 pp. 715–723, 2006.</ref>