C18

Question 1

MISCELLANEOUS ANTIMICROBIAL

AGENTS?

Answer 1

Metronidazole
Fidaxomicin
Rifaximin

Question 2

Metronidazole MOA?

Answer 2

• undergoes a reductive bioactivation of their nitro group by ferredoxin (present in anaerobic parasites) to form reactive cytotoxic products that interfere with nucleic acid synthesis

Question 3

Metronidazole PharmacoKinetix?

Answer 3

• bioavailability: effective orally
• Distribution: to most tissues (also CNS)
• can also be given intravenously
• available in topical formulations
• Elimination: hepatic metabolism
• dosage reduction may be needed in patients with liver dysfunction

Question 4

MEtronidazole Clinical use?

Answer 4

AntiBacterial:
- greatest activity against Bacteroides and Clostridium

• against pseudomembranous colitis
• effective in anaerobic or mixed intra-abdominal infections and in brain abscess
• used in the regimens for the eradication of Helicobacter pylori in gastric ulcers

AntiProtozoal:

• trichomoniasis
• giardiasis
• intestinal amebiasis
• amebic hepatic abscess

Question 5

Metronidazole toxicity?

Answer 5

• gastrointestinal irritation
• headache
• leukopenia
• Opportunistic fungal infections may occur during treatment
• Drug interactions: potentiation of coumarin anticoagulant effects

Question 6

Fidaxomicinn MOA?

Answer 6

• narrow-spectrum
• antibiotic that is active against G+ aerobes and anaerobes
• inhibits bacterial RNA polymerase

Question 7

Fidaxomycin Clinical uses and toxicity?

Answer 7

• used for C difficile infection in adults

- Toxicity is negligible due to limited absorptio

Question 8

Rifaximin MOA?

Answer 8

• derivative of rifampin
• it is active against G+ and G- aerobes and anaerobes
• inhibits DNA-dependent RNA polymerase

Question 9

Rifaximin Clinical use?

Answer 9

• management of hepatic encephalopathy
• irritable bowel syndrome with diarrhea
• adjunct in cases of refractory C difficile infection in adults

Question 10

Rifaximin Toxicity?

Answer 10

negligible due to limited absorption