In vitro activity: Meclizine is a histamine H1 receptor antagonist used to treat nausea and motion sickness, possesses anticholinergic, central nervous system depressant, and local anesthetic effects. Meclizine is an agonist ligand for mouse CAR (constitutive androstane receptor), and an inverse agonist for human CAR. Meclizine increases mCAR transactivation in a dose-dependent manner, stimulates binding of steroid receptor coactivator 1 to the murine receptor in vitro. In contrast, meclizine suppresses hCAR transactivation and inhibits the phenobarbital-induced expression of the CAR target genes, cytochrome p450 monooxygenase (CYP)2B10, CYP3A11, and CYP1A2, in primary hepatocytes derived from mice expressing hCAR, but not mCAR.

Cell Assay: HepG2 cells are cultured in 24-well dishes with DMEM supplemented with 10% charcoal-stripped calf serum. Cells are transfected using calcium phosphate with 100 ng of receptor expression vectors, 300 ng of luciferase reporter plasmids, and 100 ng of pSV2-β-galactosidase as internal control of transfection efficiency. Drugs are added 12 h after transfection, and cells are incubated for an additional 24 h. The cell lysate is assayed for luciferase activity and normalized to β-galactosidase activity.

J Pharmacol Exp Ther. 1965 Mar;147:391-8; Mol Endocrinol. 2004 Oct;18(10):2402-8.