Table 2

Kinetic parameters for ritonavir metabolism by individual liver (LMS) and enterocyte (EMS) microsomes and expressed CYP enzymes

Microsomes	K_M	V_max
	μM	pmol/min/mg
LMS 4	0.99^2-a	20.3^2-a
LMS 9	0.85^2-a	22.1^2-a
LMS 10	0.91^2-a	17.8^2-a
Mean ± SD	0.92 ± 0.07	20.1 ± 2.2

EMS 12	0.012	64.1
EMS 13	0.099	157.1
EMS 15	0.077	46.8
Mean ± SD	0.063 ± 0.045	89.4 ± 59.3

CYP2D6	1.0^2-a	0.93^a,b
CYP3A4	0.068	1.37^2-b
CYP3A5	0.047	1.00^2-b

↵2-a Calculated for the formation of R3.
↵2-b V_max, nmol product/min/nmol CYP.