Table 2

Summary of probe substrate metabolic reactions used in in vitro drug metabolism studies

P450	Preferred Substrate Reaction	K_m	Recommended Organic Solvent^2-a
		μM	<1%, v/v
1A2	PhenancetinO-deethylation	10–50	DMSO, methanol
2A6	Coumarin 7-hydroxylation	0.5–2	DMSO, methanol
2B6	S-mephenytoinN-demethylation	1900	N.R.
2C9	Tolbutamine 4′-hydroxylation	100–200	Acetonitrile
	S-Warfarin 7′-hydroxylation	1–5	N.R.
2C19	S-mephenytoin 4′-hydroxylation	31–340	Acetonitrile, methanol
2D6	Bufuralol 1′-hydroxylation	4–10	Acetonitrile
	DextromethorphanO-demethylation	2–10	DMSO, acetonitrile, methanol
2E1	Chlorzoxazone 6-hydroxylation	40	Acetonitrile
3A4/5	Testosterone 6β-hydroxylation	50–100	Acetonitrile, methanol
	Midazolam 1′-hydroxylation	3–5	N.R.

N.R., not reported.
↵2-a Effect less than 20% is deemed acceptable. Recommendation is based on at least two consistent experimental results available in the studies by Draper et al., (1997), Chauret et al., (1998), Hickman et al., (1998), Busby et al., (1999), orTang et al., (2000), with the exception of bufuralol 1′-hydroxylation in incubation with acetonitrile, which is only reported by Busby et al. (1999) in cDNA-expressed enzymes.