TABLE 3

Experimentally determined IC₅₀ values based on the initial or final inhibitor concentration and the ratio of IC₅₀ values determined with dilution (10–40-fold) versus no dilution for fluconazole, a direct-acting inhibitor of CYP3A4, and methimazole and diltiazem, metabolism-dependent inhibitors of CYP3A4 based on midazolam 1′-hydroxylation (4 μM)

All values were rounded to two significant figures. [HLM] indicates microsomal protein concentration before and after dilution. [Initial] refers to initial or predilution concentrations of inhibitor; [Final] refers to final or postdilution concentrations.

Dilution Factor	[HLM]	IC₅₀
		Fluconazole (30 min)				Methimazole (30 min)				Diltiazem (30 min)
		Without NADPH		With NADPH		Without NADPH		With NADPH		Without NADPH		With NADPH
		[Initial]	[Final]	[Initial]	[Final]	[Initial]	[Final]	[Initial]	[Final]	[Initial]	[Final]	[Initial]	[Final]
	mg/ml	μM
0	0.05 → 0.05	5.6	5.6	6.6	6.6	570	570	80	80	89	89	18	18
10	0.5 → 0.05	55	5.5	71	7.1	5100	510	76	7.6	780	78	12	1.2
20	1.0 → 0.05	110	5.3	130	6.4	4300	220	71	3.6	1100	57	9.3	0.47
30	1.5 → 0.05	160	5.4	210	6.9	8400	280	64	2.1	1700	58	8.2	0.27
40	2.0 → 0.05	280	6.9	330	8.1	10000	260	59	1.5	2100	52	8.3	0.21