EVIDENCE-BASED ANSWER
Either oral or vaginal metronidazole or vaginal clindamycin provides equivalent treatment for bacterial vaginosis in nonpregnant women (Table). Oral clindamycin 300 mg twice daily for 7 days is an effective alternative. There is conflicting evidence regarding the efficacy of a single 2-g dose of oral metronidazole. Ofloxacin 200 mg or 300 mg twice daily is less effective but could be considered for women with intolerance to metronidazole or clindamycin. Overall recurrence rates of up to 30% have been reported. (Grade of recommendation: A, based on systematic reviews and randomized controlled trials)
Evidence summary
One systematic review calculated cure rates from 5 randomized controlled trials comparing oral metronidazole, clindamycin 2% vaginal cream, and metronidazole 0.75% vaginal gel.2 Cumulative cure rates at 5 to 10 days and 4 weeks post-treatment were essentially equal for all treatments Table 1. The most common side effects were vaginal Candida infections (for both treatments) and gastrointestional symptoms (for metronidazole tablets and gels).
Metronidazole 0.75% gel used once daily for 5 days had equal efficacy compared with twice-daily dosing (cure rate = 77% vs 80%).3 One study found a cure rate of 94% with oral clindamycin 300 mg twice daily for 7 days and 96% with metronidazole 500 mg twice daily for 7 days.
A meta-analysis of 10 clinical trials compared different dosing regimens of oral metronidazole.4 The results showed comparable cure rates (85% to 87%) among groups treated with either a single 2-g dose or 500 mg twice daily for 7 days. A systematic review showed a significantly lower cure rate with a single 2-g dose compared with the 7-day regimen (54% vs 88%).5
Metronidazole (400 mg or 500 mg twice daily) achieved significantly higher cure rates compared with ofloxacin (200 mg or 300 mg twice daily) 1 to 7 days post-treatment.6,7 One review reports that ampicillin and erythromycin are ineffective and ampicillin sulbactam and ciprofloxacin are less effective than oral metronidazole.8 A systematic review of 4 studies on treatments to restore depleted Lactobacilli concluded that “these trials do not constitute enough evidence to recommend using yogurt or Lactobacillus to cure vaginal infections.”9 One systematic review of 6 randomized controlled trials found no benefit from treating male partners of women with bacterial vaginosis.10
Recommendations from others
The Clinical Effectiveness Group and the American College of Obstetricians and Gynecologists recommend: (1) 2% clindamycin cream 5 g at bedtime for 7 days or 300 mg orally twice daily for 7 days; or (2) metronidazole gel, 0.75% 5 g twice daily for 5 days or 500 mg orally twice daily for 7 days.11,12
CLINICAL COMMENTARY
Robert Pierce, MD, MSPH
Fulton Family Health Associates, Missouri
The evidence presented is consistent with my practice of treating patients with bacterial vaginosis. I treat the vast majority of patients with metronidazole 500 mg orally twice daily for a week. Sometimes I prescribe clindamycin cream or metronidazole gel, but patients seem to prefer oral therapy, despite the higher likelihood of side effects. I usually reserve oral clindamycin for treatment of bacterial vaginosis in pregnant women. I have avoided the use of single 2-g dose of metronidazole, believing it to be less effective than alternatives. I will reconsider this practice given the favorable comparisons presented here.