Table 1.

Effect of cytochrome enzyme metabolism state on serum antipsychotic level and its association with tardive dyskinesia

Cytochrome enzyme	Antipsychotic	Serum antipsychotic level PM compared to EM	Serum antipsychotic level UM compared to EM	Metabolizer group associated with TD
CYP2D6	Aripiprazole	60% higher serum level46, 1.6 fold increase in active metabolite46,47		NSD
	Clozapine	No difference47,156–158	No difference157,158	NSD
	Haloperidol	Increased serum haloperidol and metabolite levels38–42,44,45,159		No association with TD44
	Risperidone	Increased serum risperidone42,48		No association with TD58,59
	Zuclopenthixol	1.6–2 fold increased serum level49–52		Conflicting results. PM associated with TD in one study,51 another found no association with TD58,59
	Perphenazine	2.9–4 fold increased serum level54,160		No association with TD58,59
	Thioridazine	1.8–4.5 fold increased serum level55–57		NSD
	Olanzapine	No difference161		No association with TD58,59
CYP1A2	Olanzapine	No difference161		No association with TD58,59
CYP3A4	Thioridazine	1.8–4.5 fold increase serum level55–57		NSD
	Aripiprazole	1.5–1.8 fold increase in serum level, 1.6 fold increase in active metabolite46		NSD
	Ziprasidone	NSD		NSD
	Olanzapine	NSD	Subtherapeutic serum olanzapine level162	NSD

Abbreviations: PM, poor metabolizer; EM, extensive metabolizer; UM, ultrafast metabolizer; TD, tardive dyskinesia; NSD, no studies done.