Metronidazole Use in Infections

Introduction to Metronidazole

• Metronidazole is a 5-nitroimidazole antimicrobial agent with selective activity against anaerobic microorganisms, including bacteria and protozoa, and is bactericidal at low concentrations against most anaerobic bacteria, particularly effective against Bacteroides fragilis, but has no activity against aerobic bacteria 1, 2

Anaerobic Bacterial Infections

• The World Health Organization recommends metronidazole for treating anaerobic bacterial infections, including intra-abdominal infections in combination with other antibiotics, with a strength of evidence rated as high 1, 2
• The Infectious Diseases Society of America recommends metronidazole for treating Clostridioides difficile infection, with a strength of evidence rated as moderate 3, 4, 5

Protozoal Infections

• The Centers for Disease Control and Prevention recommends metronidazole for treating Trichomoniasis, with a strength of evidence rated as high 6

Bacterial Vaginosis

• The American College of Obstetricians and Gynecologists recommends metronidazole 500 mg orally twice daily for 7 days or metronidazole gel 0.75% intravaginally once daily for 5 days for treating bacterial vaginosis, with a strength of evidence rated as moderate 6

Lactobacillus Infections

• The European Society of Clinical Microbiology and Infectious Diseases states that metronidazole is not effective against Lactobacillus species and may even stimulate their growth at certain concentrations, with a strength of evidence rated as low [no citation, but implied by the context]