TABLE 2

Kinetic parameters for the formation of 1,2 diol, 21(R)-OH montelukast, 21(S)-OH montelukast, and 25-OH montelukast from montelukast in expressed in CYP2C8, CYP2C9, and CYP3A4

The kinetic parameters for the formation of montelukast metabolites were estimated by fitting the velocity versus substrate concentration to a single-site Michaelis-Menten equation.

	CYP2C8			CYP2C9			CYP3A4
Metabolites	V_max	K_m	CL_int	V_max	K_m	CL_int	V_max	K_m	CL_int
Montelukast 1,2 diol	0.015	0.31	0.05	0.048	0.53	0.091	—	—	—
21(R)-OH montelukast	—	—	—	—	—	—	0.011	3.41	0.003
21(S)-OH montelukast	—	—	—	—	—	—	0.002	3.25	0.0007
25-OH montelukast	0.002	0.33	0.006	0.005	0.59	0.009	0.002	3.89	0.0006

V_max, pmol/min per picomole of protein; K_m, μM; Cl_int, μl/min per picomole of protein