Cytochrome p450 3A4 messenger ribonucleic acid induction by rifampin in human peripheral blood mononuclear cells: correlation with alprazolam pharmacokinetics.

Objective: There is significant interest in the assessment of the individual cytochrome p450 (CYP) 3A4 activity. We analyzed whether CYP3A4 messenger ribonucleic acid (mRNA) concentrations in leukocytes reflect CYP3A activity in the liver measured by alprazolam as an in vivo probe drug. We also wanted to identify whether genetically determined high CYP3A5 expression is associated with increased alprazolam clearance.