Table 2

The IC₅₀ and K_i values of six drugs tested for the formations of LMA7 from rokitamycin and LMVfrom LMA7 with human liver microsomes

Drugs	Formation of LMA7 from Rokitamycin^2-a		Formation of LMV fromLMA7^2-a
Drugs	IC₅₀	K_i	IC₅₀	K_i
	μM		μM
Promethazine	83 ± 3^2-b	35^2-c	75 ± 13^2-b	87^2-c
Terfenadine	273 ± 127^2-b	87^2-c	33 ± 6^2-b	22^2-c
Mequitazine	>1000	ND	179 ± 65^2-b	134^2-c
Theophylline	>1000	ND	>1000	ND
Chlorpheniramine	>1000	ND	^2-d	ND
Diphenhydramine	^2-d	ND	687 ± 146	ND

↵2-a Substrate concentration of rokitamycin andLMA7 was set at 5 μM for determination of IC₅₀.
↵2-b The IC₅₀ values were expressed as the mean ± S.D. obtained from three to four different human liver microsomes.
↵2-c The K_i values were determined by Dixon plots with a pooled microsomal sample obtained from six different human livers.
↵2-d Interfered with the assay.
ND, not determined.