Consistent with this, clinical studies have shown that rifampicin, an active PXR ligand in humans, upregulates PXR activation-mediated phase II UDP-glucuronosyltransferase 1A1 (UGT1A1) and resistance-associated protein 2 (MRP2), contributing to therapeutic effects on cholestasis 14. This evidence concerns the gene UGT1A1 and cholestasis.