Antimicrobials

Active against:

• Most anaerobes including: Bacteroides fragilis and other Bacteroides spp., Clostsridium spp., Peptostreptococcus, Peptococcus, Fusobacterium

Not active against:

• Aerobic bacteria, Actinomyces spp., Propionibacterium acnes

Appropriate Uses:

• Anaerobic infections, including the following:
  • Mild cases of C. Difficile colitis (vancomycin is preferred for moderate to severe colitis)
  • Intra-abdominal infection (in combination with agents active against aerobic gram negative bacteria)
  • Anaerobic infections of bone, joint, head and neck, central nervous system and skin and soft tissue (combination therapy)
  • Surgical prophylaxis

Inappropriate Uses:

• Uncomplicated aspiration pneumonia in patients receiving beta-lactam agents that have activity against oral anaerobes (e.g., cefuroxime, ceftriaxone, meropenem, penicillin, piperacillin-tazobactam)

• Metronidazole inhibits cytochrome P450 enzyme 2C9 and may elevate blood levels of drugs metabolized via this route (e.g., fluvastatin, phenytoin, sulfonylureas, warfarin)
• Alcohol intolerance: a disulfuram reaction (nausea, vomiting, abdominal cramps, flushing and headache) may occur in some patients who drink alcohol during, or within a few days after stopping, therapy
• Pregnancy: not expected to increase risk of major congenital malformations. The theoretical risk suggested by in vitro and animal studies has not been observed in clinical experience.
• Breastfeeding: not expected to cause adverse effects in breastfed infants.
  • Infant dose via breast milk is lower than therapeutic dose used in infants.
  • Some recommend discontinuing breatfeeding for 12 to 24 hours after single-dose (e.g., 2 g) maternal treatment of Trichomonas infection.
  • Monitor nursing infant for GI symptoms.

• Nausea, anorexia, vomiting, epigastric discomfort, metallic taste
• Peripheral neuropathy and/or autonomic and/or optic neuropathy and/or metronidazole cerebellar syndrome with encephalopathy with courses longer than two weeks and/or high dosage; seizures are rare

• Usual dosage: 500 mg IV or PO q12h
  • Note: IV doses > 1g/day are automatically converted to 500 mg q12h
  • Exception: 500 mg IV q8h may be used to treat brain abscess or C. Difficile colitis in NPO patients

• C. difficile colitis: mild disease can be treated with 500 mg PO q8h for 10 – 14 days
  • Note: if oral route not feasible due to ileus or bowel obstruction, may treat with IV metronidazole 500 mg q8h (not q12h) and consider rectal administration of vancomycin

• Renal insufficiency: no reduction required

• Intermittent Infusion: Infuse over 30 – 60 minutes
• Please refer to IV drug monograph on pharmacy intranet page for additional administration information.