Prediction of response to chlorpromazine treatment in schizophrenics

A dose of 50 mg of chlorpromazine (CPZ) was given to 6 untreated schizophrenic patients and 8 healthy volunteers at 7:00 a.m. before breakfast. Blood samples were taken 3, 6, 9 and 24 hrs after for the analyses of CPZ and its metabolites by gas chromatographic techniques. In the cases of schizophrenic patients, the CPZ treatment was continued. Serum drug levels were monitored and clinical response assessed. The drug levels in serum of another group of patients already under long term treatment were also determined. Although wide inter-patients variations in serum drug levels after a single dose administration were observed, the CPZ level in the patients decreased faster than in the normal subjects. Patients showing high levels of the metabolites such as demethylated CPZ and CPZ sulfoxide after a single dose of CPZ tended to achieve poorer clinical improvement in CPZ therapy, agreeing with the results that poor responders to long term CPZ treatment revealed relatively high levels of the metabolites of CPZ compared with CPZ level. The results indicate that the study of a single dose administration prior to initiating treatment with CPZ can be used to determine how an individual patient would respond to CPZ therapy and be a valuable tool in the rational pharmacotherapy of schizophrenic patients.