Drugs acting on the gastrointestinal system

Treatment of Cl. difficile colitis or pseudomembranous colitis

• Oral Vancomycin or fidaxomicin are first line drugs for initial episodes
• Metronidazole recommended only for non severe cases when other drugs are not available or cannot be used
• Fulminant* cases treated with oral vancomycin plus intravenous metronidazole
• Recurrent cases use vancomycin or fidaxomicin or rifaximin or fecal transplant
• Bezlotoxumab is a monoclonal antibody that binds to C.difficile toxin B and is used as a preventive measure to reduce recurrences in high risk patients

*fulminant cases present with hypotension, shock, ileus or megacolon

Fidaxomicin is a macrolide antibacterial drug that is bactericidal against C difficile and inhibits bacterial RNA synthesis by RNA polymerases. Rifaximin is a similar drug.

Treatment of H.pylori: First line therapies include triple therapy with clarithromycin, proton pump inhibitor and either amoxicillin or metronidazole. Bismuth quadruple therapy includes bismuth subcitrate, a tetracycline, proton pump inhibitor (PPI) and metronidazole. Non bismuth based quadruple therapy has amoxicillin, PPI, clarithromycin and metronidazole. Some regimens use levofloxacin.