Despite several decades of research, treatment of schizophrenia still relies on a trial-and-error principle. Inadequate treatment with several antipsychotic drugs often cause prolonged hospitalizations, loss of function and decreased life quality of patients suffering from schizophrenia. In schizophrenia, up to 30 % of patients are classified with treatment resistant schizophrenia. Treatment resistant schizophrenia is characterized as insufficient response to two or more conventional antipsychotic drugs. Approximately 50 % of patients suffering from treatment resistant schizophrenia still respond to clozapine despite resistance to other antipsychotic drugs. Despite clozapines superiority in treating treatment resistant schizophrenia, clozapine is not a first line drug. Clozapine can cause rare, but life threatening side-effects. Thus patients are monitored thoroughly while being treated with clozapine, due to these side-effects. Patients would greatly benefit if clozapine response could be predicted. Thus adequate treatment could be initiated faster and the prognosis of patients would improve. The pharmacogenetics of clozapine might be the key in finding a predictor of response, since response to clozapine have been associated genetic variation in several studies.
After a thorough review of all the dopamine receptor genes, the pharmacogenetic aspects of the dopamine D2 receptor were investigated to clozapine response. No association was found in the sample.