Table 1

IC₅₀ values (μM) for inhibition of CYP3A activities in human liver microsomes

	Testosterone 6β-Hydroxylase		Midazolam 1′-Hydroxylase
	Without NADPH	With NADPH	Without NADPH	With NADPH
Amlodipine	40	4.9	43	4
Diltiazem	78	5.0	>150	15
Felodipine	32	13	27	14
Nicardipine	1.7	0.9	4.1	1.3
Nifedipine	23	27	38	47
Verapamil	20	1.8	11	4
Mibefradil	0.4^1-a	0.3^1-a	ND^1-b	0.2
Ketoconazole	0.08	0.3	0.12	ND
TAO	47	0.4	28	0.4

Incubations were performed in duplicate for each concentration of inhibitors by preincubation of inhibitors with or without NADPH for 30 min before adding the substrates.

↵1-a Data were obtained from Prueksaritanont et al., 1999.
↵1-b Not determined.