Rifaximin

Rifaximin (50 μM) reduces changes in the production of proinflammatory factors caused by LPS stimulation in IEC, such as TNF-α, IL-8, Rantes and PGE2 in normal intestinal epithelial cells. Rifaximin inhibits the LPS-induced cytokine and chemokine expression by suppressing NF-κB DNA-binding activity. Rifaximin (100 μM) effectively decreases the expression of TNFα, IL-8, MIP-3α and Rantes induced by LPS stimulation (100 μg/mL). ^[1] Rifaximin binds the β subunit of the bacterial DNA-dependent RNA polymerase, inhibiting the initiation of chain formation in RNA synthesis. Rifaximin has a lower MIC against gram-positive bacteria, with an MIC90 at dosages ranging from 0.01 µg/mL to 0.5 µg/mL. Rifaximin has broad-spectrum activity against aerobic and anaerobic gram-positive and gram-negative microorganisms. ^[2]

Rifaximin is highly concentrated in the intestinal tract compared with rifampicin. Rifaximin treatment results in significant induction of PXR target genes in the intestine of hPXR mice, but not in wild-type and Pxr-null mice. Rifaximin-mediated activation of human PXR, but not the other xenobiotic nuclear receptors constitutive androstane receptor, peroxisome proliferator-activated receptor (PPAR)alpha, PPARgamma, and farnesoid X receptor. ^[3] Rifaximin could lead to PXR-dependent hepatocellular fatty degeneration as a result of activation of genes involved in lipid uptake, thus indicating a potential adverse effect of rifaximin on liver function after long-term exposure. ^[4]