Efficacy of Oral Metronidazole with Vaginal Clindamycin or Vaginal Probiotic for Bacterial Vaginosis: Randomised Placebo-Controlled Double-Blind Trial

Background: To determine if oral metronidazole (MTZ-400mg bid) with 2% vaginal clindamycin-cream (Clind) or a Lactobacillus acidophilus vaginal-probiotic containing oestriol (Prob) reduces 6-month bacterial vaginosis (BV) recurrence. Methods: Double-blind placebo-controlled parallel-group single-site study with balanced randomization (1∶1∶1) conducted at Melbourne Sexual Health Centre, Australia. Participants with symptomatic BV [Nugent Score (NS) = 7–10 or ≥3 Amsel's criteria and NS = 4–10], were randomly allocated to MTZ-Clind, MTZ-Prob or MTZ-Placebo and assessed at 1,2,3 and 6 months. MTZ and Clind were administered for 7 days and Prob and Placebo for 12 days. Primary outcome was BV recurrence (NS of 7–10) on self-collected vaginal-swabs over 6-months. Cumulative BV recurrence rates were compared between groups by Chi-squared statistics. Kaplan-Meier, log rank and Cox regression analyses were used to compare time until and risk of BV recurrence between groups. Results: 450 18–50 year old females were randomized and 408 (91%), equally distributed between groups, provided ≥1 NS post-randomization and were included in analyses; 42 (9%) participants with no post-randomization data were excluded. Six-month retention rates were 78% (n = 351). One-month BV recurrence (NS 7–10) rates were 3.6% (5/140), 6.8% (9/133) and 9.6% (13/135) in the MTZ-Clind, MTZ-Prob and MTZ-Placebo groups respectively, p = 0.13. Hazard ratios (HR) for BV recurrence at one-month, adjusted for adherence to vaginal therapy, were 0.43 (95%CI 0.15–1.22) and 0.75 (95% CI 0.32–1.76) in the MTZ-Clind and MTZ-Prob groups compared to MTZ-Plac respectively. Cumulative 6-month BV recurrence was 28.2%; (95%CI 24.0–32.7%) with no difference between groups, p = 0.82; HRs for 6-month BV recurrence for MTZ-Clind and MTZ-Prob compared to MTZ-Plac, adjusted for adherence to vaginal therapy were 1.09(95% CI = 0.70–1.70) and 1.03(95% CI = 0.65–1.63), respectively. No serious adverse events occurred. Conclusion: Combining the recommended first line therapies of oral metronidazole and vaginal clindamycin, or oral metronidazole with an extended-course of a commercially available vaginal-L.acidophilus probiotic, does not reduce BV recurrence. Trial Registration: ANZCTR.org.au ACTRN12607000350426