Table 3.

Interaction of ziprasidone, risperidone and 9-hydroxyrisperidone with human liver cytochromes P450: IC₅₀values for inhibition of probe substrate activities.

	IC50 value (μm)a
CYPb	Ziprasidone	Risperidone	9-Hydroxy-risperidone
CYP1A2	>100	>100	>100
CYP2C9	>100	>100	>100
CYP2C19	>100	>100	52c
CYP2D6	31 ± 37	14 ± 9	31 ± 11
CYP3A4	72 ± 29	75 ± 16	90 ± 5

^aIC₅₀ values <100 μm were determined from Y=100–(100X/(X+B)), where X=inhibitor concentration and B = IC₅₀. Values aremean± s.d. (n = 3).

^bCYP=cytochrome P450.

^cMean of two values. One set of human liver microsomes hadlow CYP2C19 activity.