Table 2

In vitro inhibition of CYP2D6-catalyzed dextromethorphan O-demethylation by antipsychotic drugs

Antipsychotic Drug	Type of Inhibition	K_i
		μM
Perphenazine^2-b	Partial Competitive	0.8 ± 0.4^2-a
Thioridazine^2-b	Partial Competitive	1.4 ± 0.8
Chlorpromazine	Competitive	6.3 ± 3.8
Haloperidol^2-b	Partial Competitive	7.2 ± 4.9
Fluphenazine	Competitive	9.4 ± 1.5
Risperidone	Competitive	21.9 ± 1.7
Clozapine	Competitive	39.0 ± 14.4
cis-Thiothixene	Competitive	65.0 ± 42.7

↵2-a Each value indicates mean ± S.D. obtained from three different livers.
↵2-b Mean (S.D.) of α, a factor by which K_mchanges when inhibitor occupies the enzyme: perphenazine, 22.2 ± 1.6; thioridazine, 72.5 ± 28.9; haloperidol, 5.7 ± 1.9.