Table 1

IC₅₀ values for the effect of various inhibitors on the BL to AP transport of digoxin across Caco-2 and LLC-MDR1 cell monolayers and for midazolam hydroxylation activity in CYP3A4-expression system^1-a

Inhibitor	Caco-2	LLC-MDR1	CYP3A4-Expression System
Ketoconazole	1.50	—^1-b	0.0340
Verapamil	16.8	224	10.3
L754.394	>3^1-c	>3^1-d	0.0182
Valspodar	0.114	0.0222	7.06

↵1-a Data represent IC₅₀ values defined as the concentration of inhibitors (μM) necessary to induce a 50% inhibition of digoxin transport (Fig.3) and midazolam hydroxylation activity (Fig. 1).
↵1-b No inhibitory effect was observed up to 3 μM ketoconazole.
↵1-c 89.2 ± 7.7% of control at 3 μM L754.394.
↵1-d 72.0 ± 9.5% of control at 3 μM L754.394.