TABLE 2

Percentage change in inhibition of human P450 enzymes with a 30-min incubation of inactivator, human liver microsomes, and NADPH

Inactivator	Enzyme Known to Be Inactivated	Percentage Decrease in Activity at IC₂₅
Inactivator	Enzyme Known to Be Inactivated			CYP1A2	CYP2B6	CYP2C8	CYP2C9	CYP2C19	CYP2D6	CYP3A(M)^a	CYP3A(T)^a
Furafylline	CYP1A2	55	—^b	—	—	25	28	—	—
Zileuton	CYP1A2	41	—	—	—	—	—	—	—
PPP	CYP2B6	—	54	—	—	—	—	—	—
thioTEPA	CYP2B6	—	46	38	16	13	—	50	32
Desethylamiodarone	CYP2C8	—	21	30	36	—	21	29	25
Tienilic acid	CYP2C9	—	—	—	59	—	—	—	—
Ticlopidine	CYP2C19	21	43	—	—	11	—	35	19
MDMA	CYP2D6	25	25	—	—	—	59	—	—
Paroxetine	CYP2D6	—	—	—	—	—	62	24	29
Diltiazem	CYP3A	—	—	—	—	—	—	37	43
Erythromycin	CYP3A	—	—	—	—	—	—	43	67
Ritonavir^c	CYP3A	—	—	—	—	—	—	—	—
Verapamil	CYP3A	—	—	—	—	—	—	49	63
Montelukast	None	—	—	—	—	—	—	—	—

↵ a CYP3A(M) and CYP3A(T) refer to midazolam and testosterone hydroxylase activities, respectively.
↵ b —, the decrease in activity was less than 15%, except for CYP2C19, which was <10%.
↵ c It should be noted that ritonavir shows less than 15% in activity with preincubation. This is likely because of the extremely potent reversible inhibition caused by this compound.