A Randomized Trial of Metronidazole in Asymptomatic Bacterial Vaginosis to Prevent the Acquisition of Sexually Transmitted Diseases

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ABSTRACT Bacterial vaginosis (BV)—the most common form of vaginitis throughout the world—has been associated with adverse outcomes including HIV infection and other sexually transmitted diseases (STDs). One reason for this may be the absence of hydrogen peroxide-producing lactobacilli that inhibit bacterial growth. At present, treatment of asymptomatic BV is not routinely recommended. This goal of this prospective study was to determine whether treating BV lessens the risk of STDs. Participants were 107 African American women with asymptomatic BV whose mean age was 25 years. Fifty-three of them were assigned randomly to apply intravaginal metronidazole gel at bedtime for 5 days and subsequently twice a week for 6 months. These women and the 54 who were only observed were followed up for a total of 12 months. Significantly longer times preceded the development of STD in women using metronidazole gel. Six-month rates of STD were 2.29 per person-year in the observed group and 1.58 per person-year in the actively treated women, a statistically significant difference. No such difference was apparent in the last 6 months of the study after treatment ended. Overall rates of STD for the entire 12-month period were 1.64 and 1.31, respectively, in the observation and treatment groups. The only significant difference in the distribution of individual pathogens was a greater frequency of chlamydia infection in the observed group. This is the first study to demonstrate that the prevention and treatment of asymptomatic BV lowers the risk of chlamydia infection. While it remains necessary to confirm these findings, especially in more diverse populations, the present findings suggest that routine treatment be considered for women with BV even if there are no symptoms.