What is the recommended dose of metronidazole (Flagyl) for bacterial vaginosis?

Metronidazole Dosing for Bacterial Vaginosis

The recommended dose of metronidazole for bacterial vaginosis in non-pregnant women is 500 mg orally twice daily for 7 days. 1, 2

Standard Treatment Regimens

First-Line Oral Therapy

• Metronidazole 500 mg orally twice daily for 7 days is the CDC-recommended standard treatment, achieving cure rates of approximately 78% and providing systemic coverage for potential subclinical upper tract infection 2, 3
• This 7-day regimen is superior to single-dose therapy in terms of sustained cure rates 2

Alternative Oral Regimen

• Metronidazole 2 g orally as a single dose is an alternative option, though it has lower efficacy compared to the 7-day course 2
• The single-dose regimen may be associated with higher relapse rates and should be reserved for situations where adherence to multi-day therapy is unlikely 4

Topical Alternatives

• Metronidazole gel 0.75%, one full applicator (5 g) intravaginally once daily for 5 days, is an effective alternative that minimizes systemic side effects 2
• The vaginal gel achieves less than 2% of the blood levels compared to oral medication, avoiding gastrointestinal upset and metallic taste while maintaining local efficacy 1, 2

Critical Safety Warning

Patients must completely avoid all alcoholic beverages during metronidazole treatment and for at least 24 hours after the last dose to prevent severe disulfiram-like reactions. 1, 2

Special Population Dosing

Pregnant Women

• For pregnant women, metronidazole 250 mg orally three times daily for 7 days is the recommended regimen, using a lower dose to minimize fetal exposure while providing systemic coverage 1, 2, 5
• Metronidazole is contraindicated in the first trimester of pregnancy; clindamycin vaginal cream should be used instead during this period 2
• Alternative regimens for pregnant women include metronidazole 2 g single dose or clindamycin 300 mg orally twice daily for 7 days 1

HIV-Infected Patients

• Use the same treatment regimens as for HIV-negative patients, including metronidazole 500 mg orally twice daily for 7 days 1

Common Pitfalls to Avoid

• Do not use metronidazole gel for trichomoniasis (efficacy <50%), as it is only effective for bacterial vaginosis 6
• Avoid self-treatment with over-the-counter products, as they are ineffective for bacterial vaginosis 1
• Sexual partners do not require treatment, as multiple clinical trials demonstrate that treating partners does not improve cure rates or prevent recurrence 1, 2

Expected Side Effects

• Mild gastrointestinal upset and unpleasant metallic taste are common with oral metronidazole 1
• Topical gel formulations avoid these systemic side effects while maintaining efficacy 1, 2

Follow-Up Considerations

• No follow-up visit is necessary if symptoms completely resolve 1, 2
• Recurrence is common, with up to 50% of women experiencing bacterial vaginosis again within one year 1
• If symptoms return, retreatment with a recommended regimen is appropriate 1