Metronidazole

Snapshot

• A 23-year-old woman presents to her gynecologist for a wellness exam. She reports that she has been having a “fishy” vaginal odor for the past 3 days. She endorses to recently being sexually active with a new partner and does not use barrier contraception. Physical examination is notable for gray vaginal discharge that has a fishy odor. Nucleic acid amplification testing for gonorrhea and chlamydia is negative. An amine whiff test enhances the fishy odor. Vaginal fluid pH is > 4.5. There are clue cells with a stippled appearance on the outer margins on microscopic testing of the vaginal fluid. She is started on metronidazole. (Bacterial vaginosis)

Introduction

• Mechanism of action
  • free radical formation that damages bacterial DNA 
    • is bactericidal and has antiprotozoal activity
• Clinical use
  • protozoal infections
    • Giardia
    • Entamoeba
    • Trichomonas
  • anaerobic bacteria (below the diaphragm)
    • Bacteroides
    • Clostridium difficile
    • Gardnerella vaginalis
  • Helicobacter pylori
    • as part of triple therapy in patients who are penicillin allergic
• Adverse reaction
  • disulfiram-like reaction  
    • when consuming alcohol, patients can experience severe flushing, hypotension, and tachycardia