C18. Metronidazole. Fidaxomycine. Rifaximin. Pharmacotherapy of abdominal infections. Flashcards
What is the MOA of Metronidazole?
Metronidazole is a nitroimidazole. It makes toxic free radical metabolites of reductive processes in bacteria → DNA damage passive diffusion thru outer cell membrane mainly effective in anaerobic conditions.
What is the MOA of Fidaxomycine?
Fidaxomycine is similar to macrolides, but has a different MOA. It inhibits RNA polymerase.
What is the MOA of Rifaximin?
Rifaximin is a rifamycin antibiotic (group incl. rifampin, rifabutin). It inhibits RNA polymerase.
What are the side effects of metronidazole?
- GI: Nausea
- Dizziness
- Metallic taste
- Alcohol intolerance
- (after long admin in animals → carcinogenic).
What are the indications of metronidazole?
Anaerobic infections:
- 1st line for C. diff
- Brain abscess
- Peritonitis
- H. pylori - in combo
- Protozoal infections
What are the kinetic parameter like for Metronidazole?
- Orally administered
- Good tissue distribution (abscesses, CNS, etc.)
- Liver metabolism (↓ dose in hepatic disease)
- Interactions: inhibit CYP450s.
What spectrum does metronidazole cover?
Gram +/- anaerobes:
- Gram + (C. diff and other Clostridia)
- Gram - (B. fragilis)
- Protozoa: Giardia, Trichomonas, Entamoeba
- H. pylori (in combo)
Better for Gram -, whereas clindamycin is better for Gram + anaerobes → clindamycin above + metro below diaphragm.
What are the indications of Fidaxomycine?
Almost exclusive activity against C. difficile → for pseudomembranous colitis.
What spectrum does Rifaximin cover?
- Staph, Strep, Enterococci
- Some Gram -
- No Pseudomonas, acinetobacter?
What are the pharmacokinetic parameter of Rifaximin?
Orally administered for local GI effect → surgery prophylaxis + hepatic encephalopathy + traveler’s diarrhea.
What are the indications of Rifaximin?
- Surgery prophylaxis
- Hepatic encephalopathy
- Traveler’s diarrhea
Pharmacotherapy of abdominal infections??
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