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 is recommended only for non-severe cases when other drugs aren’t available or can’t be used.
• Fulminant* cases are treated with oral vancomycin plus intravenous metronidazole.
• Recurrent cases are treated with 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, a proton pump inhibitor, and either amoxicillin or metronidazole. Bismuth quadruple therapy includes bismuth subcitrate, a tetracycline, a proton pump inhibitor (PPI), and metronidazole. Non-bismuth-based quadruple therapy includes amoxicillin, a PPI, clarithromycin, and metronidazole. Some regimens use levofloxacin.