Metronidazole Gel for Bacterial Vaginosis
For bacterial vaginosis, use metronidazole gel 0.75%, one full applicator (5 grams) intravaginally twice daily for 5 days, which achieves cure rates of 75-87% and is equivalent in efficacy to oral metronidazole while causing fewer gastrointestinal side effects. 1, 2, 3
Standard Treatment Regimen
The FDA-approved dosing is one applicator (5 grams containing 37.5 mg metronidazole) intravaginally either once or twice daily for 5 days 3:
- Twice-daily dosing: One applicator morning and evening for 5 days 1, 2, 3
- Once-daily dosing: One applicator at bedtime for 5 days (equivalent efficacy to twice-daily) 3, 4
The twice-daily regimen achieves clinical cure in 75-87% of patients at 7-10 days post-treatment, with sustained cure rates of 58-71% at one month 1, 5, 6. Once-daily dosing yields comparable results: 77% cure at first follow-up and 58% at one month 4.
Critical Patient Counseling
Alcohol avoidance: Patients must avoid all alcohol consumption during treatment and for 24 hours after completion to prevent disulfiram-like reactions (flushing, nausea, vomiting, headache) 1, 7, 2, 8.
Barrier contraception warning: The gel is oil-based and may weaken latex condoms and diaphragms during the treatment period 1, 7, 2.
Allergy consideration: Patients with known allergy to oral metronidazole should NOT receive the vaginal formulation 1, 2.
When to Use Gel vs. Oral Therapy
Metronidazole gel is preferred over oral metronidazole when 1, 6, 9:
- Patient cannot tolerate systemic side effects (gastrointestinal upset occurs in 52% with oral vs. 33% with gel) 6
- Patient prefers to avoid systemic medication exposure (peak serum levels with gel are <2% of oral doses) 1
- Patient has intolerance (but not allergy) to oral metronidazole 1
However, oral metronidazole 500 mg twice daily for 7 days remains the primary recommended regimen and achieves slightly higher cure rates (84-95%) 1, 8.
Common Pitfalls to Avoid
Do NOT treat sex partners: Clinical trials consistently show that treating male partners does not influence cure rates or prevent recurrence 1, 7, 2, 8. Partner treatment is not recommended 1.
Do NOT use gel for trichomoniasis: Metronidazole gel achieves inadequate therapeutic levels in the urethra and perivaginal glands, making it ineffective for trichomonas (<50% efficacy) 1, 2. Only oral metronidazole should be used for trichomoniasis 1.
Do NOT use single-dose regimens for recurrent BV: The 2-gram single oral dose has lower efficacy (84% vs. 95% for multi-day regimens) and should be avoided in recurrent cases 7, 2, 8.
Pregnancy Considerations
Avoid metronidazole gel in pregnancy: The CDC recommends systemic therapy for pregnant women to treat possible subclinical upper genital tract infections 1. For symptomatic low-risk pregnant women, metronidazole gel 0.75% twice daily for 5 days is listed as an alternative, but oral therapy is preferred 1.
For high-risk pregnant women (prior preterm delivery), use metronidazole 250 mg orally three times daily for 7 days in the second trimester 1, 7.
Follow-Up and Recurrence
Follow-up visits are unnecessary if symptoms resolve 1, 2, 8. However, recurrence is common (42-50% within one year) 4, 10, 5.
For recurrent BV after initial treatment failure 10:
- Extended oral metronidazole: 500 mg twice daily for 10-14 days
- If still ineffective: Metronidazole gel 0.75% for 10 days, then twice weekly for 3-6 months
No long-term maintenance regimen is recommended for routine cases 1.