Debrisoquine oxidation in an Italian population: a study in healthy subjects and in schizophrenic patients.

The debrisoquine oxidation phenotype was assessed in 137 healthy Italian volunteers and in 41 drug-free schizophrenic patients. A bimodal distribution of the urinary debrisoquine/4-hydroxydebrisoquine metabolic ratio was observed in healthy volunteers. Ten subjects were identified as poor metabolizers, yielding a frequency of 7.3% which is similar to that reported in other European countries. The prevalence of the poor metabolizer phenotype was 9.8% among schizophrenic patients. This indicates that there is no association between polymorphic drug oxidation and schizophrenic disorder. Treatment with chlorpromazine (100 or 150 mg daily) significantly increased the debrisoquine metabolic ratio in nine patients (P less than 0.01). These results confirm that neuroleptics of the phenothiazine class inhibit the oxidative metabolism of debrisoquine.