When is Flagyl (metronidazole) used?

Indications for Flagyl (Metronidazole) Use

Flagyl (metronidazole) is primarily indicated for treating trichomoniasis, bacterial vaginosis, anaerobic bacterial infections, amebiasis, and giardiasis. 1, 2

Specific Indications

Protozoal Infections

• Trichomoniasis

  • Treatment of symptomatic and asymptomatic trichomoniasis in both males and females 1
  • Recommended regimen: 2g orally in a single dose 2
  • Alternative regimen: 500mg twice daily for 7 days 2
  • Treatment of asymptomatic sexual partners is recommended to prevent reinfection 1

• Amebiasis

  • Acute intestinal amebiasis (amebic dysentery)
  • Amebic liver abscess (though aspiration or drainage may still be needed) 1

• Giardiasis 1, 3

Bacterial Infections

• Bacterial Vaginosis (BV)

  • Recommended regimens:
    • Metronidazole 500mg orally twice daily for 7 days
    • Metronidazole 250mg orally three times daily for 7 days (for pregnant women) 2

• Anaerobic Bacterial Infections 1, 4

  • Intra-abdominal infections (peritonitis, abscesses)
  • Skin and skin structure infections
  • Gynecologic infections (endometritis, tubo-ovarian abscess)
  • Bacterial septicemia
  • Bone and joint infections (adjunctive therapy)
  • CNS infections (meningitis, brain abscess)
  • Lower respiratory tract infections
  • Balanoposthitis (in combination with other antibiotics) 5

Dosing Considerations

Standard Dosing Regimens

• Trichomoniasis: 2g orally in a single dose or 500mg twice daily for 7 days 2
• Bacterial vaginosis: 500mg orally twice daily for 7 days 2
• Anaerobic infections: Typically 500mg orally three times daily or 500mg IV every 6-8 hours 1
• Balanoposthitis: 500mg twice daily for 7 days (often combined with ofloxacin) 5

Special Populations

Pregnancy

• Metronidazole 250mg orally three times daily for 7 days is recommended for BV in pregnant women 2
• For trichomoniasis in pregnancy, 2g single dose may be used after first trimester 5
• Treatment is indicated for symptomatic trichomoniasis during pregnancy 2

HIV Infection

• Patients with trichomoniasis or BV who are also HIV-infected should receive the same treatment regimens as HIV-negative patients 2

Treatment Failures

• For trichomoniasis treatment failures, re-treat with metronidazole 500mg twice daily for 7 days 2
• If second treatment fails, consider metronidazole 2g once daily for 3-5 days 2
• For persistent cases, susceptibility testing may be needed 2

Important Precautions

• Avoid alcohol during treatment and for 24-48 hours afterward to prevent disulfiram-like reactions 5
• Metronidazole is bactericidal against most anaerobic bacteria, particularly effective against Bacteroides fragilis 4
• Avoid prolonged courses to minimize risk of neurotoxicity 5
• For mixed infections (aerobic and anaerobic), metronidazole should be combined with appropriate antibiotics for aerobic coverage 6

Follow-Up Recommendations

• Follow-up visits are generally unnecessary if symptoms resolve 2
• For high-risk pregnant women treated for BV, follow-up at 1 month after treatment completion may be considered 2
• Patients should abstain from sexual intercourse until they and their partners have completed treatment 5

Metronidazole remains the drug of choice for anaerobic infections due to its excellent activity, favorable pharmacokinetics, and cost-effectiveness 4.