Efficacy and Safety Study of Rifaximin Vaginal Tablets in Bacterial Vaginosis

Inclusion Criteria: * Clinical diagnosis of bacterial vaginosis with Amsel's criteria (4 out of 4 fulfilled criteria): * Off white (milky or gray), thin, homogeneous, adherent vaginal discharge * pH \>4.5 * Positive "whiff test" * Presence of clue cells ≥20% * Bacteriological diagnosis of bacterial vaginosis with Gram stain Nugent score ≥ 4 (patients may be enrolled/randomized without this result) * Post-menarchal, pre-menopausal female patient * Non-pregnant (negative urine pregnancy test at Entry Visit/V1) nor breast-feeding patient * Patient aged between 18 50 years, inclusively * Patient who is willing to be asked questions about personal medical health and sexual history * Patient capable of and willing to conform to the study protocol * Patient who have been thoroughly informed of the aim of the study and the study procedures and who provided signed and dated written informed consent form * Patient who agrees to abstain from intercourse during the 5 day treatment period * Patient who agrees also to abstain from intercourse 3 days before the scheduled visits of follow-up * Patient who agrees to abstain from the use of any other intravaginal product (i.e., douching, feminine deodorants sprays, tampons, spermicides, gels, foams, vaginal birth control ring and diaphragms) during the entire study period * Patient who agrees to use an adequate method of birth control for the duration of the study to avoid pregnancy. Acceptable methods include a history of bilateral tubal ligation, male partner with a vasectomy, a hormonal contraceptive \[oral, patch, injectable or implantable (excluding intrauterine implantable devices \[IUD\], intrauterine system \[IUS\] and vaginal rings), or abstinence * Patient who agrees to abstain from alcohol ingestion during the 5-day treatment period and for 1 day afterward Exclusion Criteria: * Virginity * Patient with other infectious causes of vulvovaginitis (e.g., candidiasis, Trichomonas vaginalis, Chlamydia trachomatis, Neisseria gonorrhoeae, active Herpes simplex lesions, or Human Papilloma Virus lesions); patients may be enrolled/randomized without these results) * Other vulvovaginal or cervical conditions, abnormalities or disorders confounding the interpretation of clinical response (including total hysterectomy) * Symptoms suggestive of pelvic inflammatory disease * Patient with intra uterine device (IUD), intrauterine system (IUS), or vaginal ring as contraceptive method * Patient with severe hepatic insufficiency (Child C) * Patient with severe cardiac insufficiency (NYHA - New York Heart Association classes 3 - 4) * Patient who will be being evaluated, including colposcopy and cervical biopsies, or being treated during the study period, for abnormal Pap test or cervical carcinoma. To note that if the Pap test will be performed at baseline, the result will be known after the randomization visit: patients may be enrolled without this result * Any condition or circumstance that would prevent completion of the study or interfere with analysis of study results, including a history of drug or alcohol abuse, mental illness or non-compliance with treatments or visits, immunological (including HIV infection), hematological or neoplastic disease (including all cervical neoplastic diseases) * Cervical cryotherapy, loop electrosurgical excision (LEEP), cervical laser, or any other ablative or excisional cervical procedures within the last 3 months * Vaginal laser within the last 3 months * Patient with clinically relevant pathological laboratory values * Known hypersensitivity to rifaximin * Known hypersensitivity to excipients present in rifaximin, placebo or metronidazole formulations * Known hypersensitivity to metronidazole, either orally or topically administered, or any forms of parabens * Concurrent anticoagulant therapy with coumadin or warfarin * Menstruating or anticipated menstruation/withdrawal bleed at Entry Visit/V1 and during the drug administration * Patient who received antifungal or antimicrobial therapy (systemic or intravaginal) within 14 days of randomization * Patient who have participated in another clinical trial or have taken an investigational drug within the last 4 weeks prior screening * Patient who has taken disulfuram within the last 14 days * Withdrawal of informed consent * Patient previously randomized in this study