Rifaximin-d₆is intended for use as an internal standard for the quantification of rifaximin by GC- or LC-MS. Rifaximin is an antibiotic derived from rifamycin SV that inhibits the growth of a variety of Gram-positive and Gram-negative bacteriain vitro, includingStaphylococcus,Streptococcus,Enterococcus,H. influenzae, andN. gonorrhoeae(MIC₅₀s = ≤0.015,<0.12, 0.25-2, 0.25, and 0.25 μg/mL, respectively).¹It is a pregnane X receptor (PXR) agonist (EC₅₀= ~20 μM) that reduces colonic damage, rectal bleeding, and diarrhea in PXR-humanized, but not wild-type orPxr-null, mice with inflammatory bowel disease (IBD) induced by dextran sulfate sodium .^2,3Rifaximin exhibits minimal intestinal absorption after oral administration and is, therefore, effective in eliminating bacteria in the gastrointestinal system.^4,5Formulations containing rifaximin have been used in the treatment of traveler's diarrhea caused by noninvasiveE. coli, irritable bowel syndrome with diarrhea (IBS-D), and to reduce the risk of recurrence of overt hepatic encephalopathy.

1.Hoover, W.W., Gerlach, E.H., Hoban, D.J., et al.Antimicrobial activity and spectrum of rifaximin, a new topical rifamycin derivativeDiagn. Microbiol. Infect. Dis.16(2)111-118(1993) 2.Ma, X., Shah, Y.M., Guo, G.J., et al.Rifaximin is a gut-specific human pregnane X receptor activatorJ. Pharmacol. Exp. Ther.322(1)391-398(2007) 3.Cheng, J., Shah, Y.M., Ma, X., et al.Therapeutic role of rifaximin in inflammatory bowel disease: Clinical implication of human pregnane X receptor activationJ. Pharmacol. Exp. Ther.335(1)32-41(2010) 4.Alajbegovic, S., Sanders, J.W., Atherly, D.E., et al.Effectiveness of rifaximin and fluoroquinolones in preventing travelers' diarrhea (TD): A systematic review and meta-analysisSyst. Rev.1:39(2012) 5.Song, M., and Ang, T.L.Second and third line treatment options for Helicobacter pylori eradicationWorld J. Gastroenterol.20(6)1517-1528(2014)