Table 1 Eligibility criteria

Must be 16–50 years old and pre-menopausal. Capable of giving written informed consent.

Younger than 16 or post-menopausal.

Fluent spoken and written English.

Menstruating at diagnosis.

Agrees to examination on enrollment day, day 17–19 and day 40–42.

Symptoms so severe as to make allocation to placebo unacceptable to the woman.

Has a negative pregnancy test during the study. Agrees to follow study protocol and is reliable for follow-up.

Currently pregnant or at high risk for pregnancy.

Has documented bacterial vaginosis infection by positive vaginal swab (minimum Nugent score of ≥7) and meets three of four Amsel criteria.

Current active sexually transmitted infection (chlamydia, gonorrhea, trichomonas).

Agrees to refrain from vaginal intercourse for the 10 days of treatment (or to use non-lubricated non-latex condoms if unavoidable). Agrees not to douche or use any intravaginal products during treatment (including tampons, medications, devices).

Current yeast infection as determined by history, physical examination, and swab analysis.

Agrees to abstain from alcohol during the 10 days of treatment (from 24 hours before through 72 hours after taking study medication).

History of pelvic inflammatory disease. Allergy to metronidazole.

Agrees to no new medications or antibiotics during treatment.

Currently breast feeding.

Has no currently active sexually transmitted infection as determined by history, physical examination, and swab analysis negative for chlamydia, gonorrhea, candidiasis, or trichomonas.

Any open wound, excoriation, or vaginal irritation, including Bartholin’s cyst, abscess, and herpes simplex viral lesion, as determined by physical exam.

Presence of another vulvar, vaginal or medical condition, including cervical neoplasia or treatment, or medical device, including intrauterine device, that might confound treatment response.

Using lithium, anticoagulants or disulfiram drugs.

Any antifungal or antibiotic use 14 days prior to enrolment.

Papanicolaou smear taken within one week of enrolment.

Meeting three of four Amsel criteria but having a Nugent score <7.