Clozapine Asians

Scharfetter etal. (1999) DRD3 (S9G) Clozapine G allele is associated with clozapine response. Schizophrenia Asian... 

CYP2D6 Antidepressants amitriptyline, clomipramine, imipramine, desipramine, nortriptyline, trimipramine, N-desmethyl-clomipramine, fluoxetine, norfluoxetine, paroxetine, venlafaxine, sertraline Neuroleptics chlorpromazine, thioridazine, perphenazine, haloperidol, reduced haloperidol, risperidone, clozapine, sertindole Others codeine, opiate, propranolol, dextromethorphan 4 no activity 25% in Caucasians 0%-10% in others 5 no activity 2%-10% in all groups 10 reduced activity 47%-70% in Asians <5% in others 17 reduced activity 25%-40% in blacks 0% in others 2XN increased activity 19%-29% in Arabs and Ethiopians <5% in others... 

A recent study of the atypical antipsychotic clozapine in Asians (Matsuda et al. 1996) found that Korean American patients showed a greater improvement than whites while receiving lower mean doses of clozapine. Korean Americans had lower mean clozapine concentrations than did Caucasians, yet they were more likely to experience anticholinergic and other side effects. No cases of agranulocytosis were reported in Korean American patients, and the incidence in Asians is not known. Clozapine is metabolized by CYP1A2, which is highly inducible, so such differences may be due to differences in diet and other personal habits. 

Findings of our study of atypical neuroleptics and antipsychot-ics show that African American patients may need a higher dose of clozapine than that required by Caucasian patients. Likewise, it appears that African Americans may need a higher dose of olanzapine than Caucasians do and that Hispanics have intermediate requirements. Asian patients appear to require the lowest dose of all, but it must be noted that the study included a relatively small sample of Asians. Finally, Hispanics may need a lower dose of risperidone than that required by African Americans or Caucasians, and the dose difference between the latter two groups may be negligible. 

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