TABLE 4

K₁ estimates for different CYP3A preparations obtained from inactivation experiments

Calculation of K₁ was based on the loss of midazolam 1′-hydroxylation activity. Experiments were conducted with at least five inhibitor concentrations, preincubation times varying from 1 to 25 min, and with 8 μM midazolam. Human liver microsomal preparations contained predominantly CYP3A4 or CYP3A5, as described under Materials and Methods. Data for microsomes are reported as mean ± S.D. (except for erythromycin and CYP3A5, where data from only two livers could be fit to the inactivation model). Values for Supersomes are mean ± S.E. for the model fit. No statistical tests were performed for comparison of Supersomes.