By William Elliott, MD, FACP, and James Chan, PharmD, PhD

Dr. Elliott is Assistant Clinical Professor of Medicine, University of California, San Francisco.

Dr. Chan is Associate Clinical Professor, School of Pharmacy, University of California, San Francisco.

Drs. Elliott and Chan report no financial relationships relevant to this field of study.

The FDA has approved the first oral single-dose treatment for bacterial vaginosis in adult women. Secnidazole is a next-generation 5-nitroimidazole prodrug that is activated after entry into bacterial cells. It was designated by the FDA as a Qualified Infectious Disease Product and was granted priority review. Secnidazole is marketed as Solosec.


Secnidazole is indicated for the treatment of bacterial vaginosis (BV) in adult women.1


The recommended dose is a single 2-gram packet of granules once daily.1 The granules should be sprinkled onto applesauce, yogurt, or pudding and taken within 30 minutes followed by a glass of water. It may be taken without regard to timing of meals.

Secnidazole is not intended to be dissolved in any liquid. It is available as 2-gram, unit-of-use, oral granules.


Secnidazole offers a single-dose oral treatment for BV. Current treatments recommended by the CDC are oral metronidazole twice daily for seven days, metronidazole vaginal gel once daily for five days, or clindamycin cream intravaginally once daily for seven days.2

Alternative regimens include oral tinidazole or clindamycin for two to seven days. Secnidazole does not produce a significant drug-drug interaction with oral contraceptives containing ethinyl estradiol and norethindrone.1


Secnidazole treatment may result in vulvovaginal candidiasis.1 In clinical trials, the frequency was 9.6% compared to 2.9% for placebo. This is the most frequently reported adverse reaction. Breastfeeding is not recommended during treatment and for 96 hours after administration.1


The efficacy of secnidazole was evaluated in two randomized, placebo-controlled studies in subjects with BV.1,3 Diagnosis of BV was defined as: the presence of an off-white (milky or gray), thin homogeneous vaginal discharge; vaginal pH ≥ 4.7; presence of clue cells ≥ 20% of the total epithelial cell on microscopic examination of the vaginal saline wet mount; a positive “whiff” test (detection of fishy odor on addition of 10% potassium hydroxide solution to a sample of vaginal discharge); and a Nugent score (gram stain scoring system) ≥ 4.1,4 Efficacy endpoints were clinical response (defined as normal vaginal discharge); negative “whiff” test and clue cells < 20%, Nugent score cure (score of 0-3); and therapeutic response, clinical response, and Nugent score cure.

At 21-30 days after randomization, clinical response rates were 67.7% for study 1 and 53.3% for study 2, with corresponding placebo rates of 17.7% and 19.3%, respectively. Nugent score cures were 40.3% and 43.9% vs. 6.5% and 5.3%, respectively. Therapeutic response rates were 40.3% and 34.6% vs. 6.5% and 3.5%. Currently, there are no comparative studies with other antibacterial agents. The results were similar to a study of oral metronidazole and oral tinidazole. For subjects with a baseline Nugent score > 7 and evaluated at the one-month follow-up visit, Nugent score cures were 35.9% for metronidazole (500 mg twice daily for seven days) and 38.1% for tinidazole (500 mg twice daily for seven days).3


BV is a polymicrobial clinical syndrome caused by replacement of Lactobacillus spp in the vagina with anaerobic bacteria (e.g., Gardnerella vaginalis, Prevotella spp, and Mobiluncus spp).2 It is the most prevalent cause of vaginal discharge. Typical treatment is oral or intravaginal treatment for seven and five days, respectively. Secnidazole is the first single-dose treatment for this common condition. It appears to have similar effectiveness to metronidazole and is well tolerated.

Cost is not available as the drug is expected to be available in the first quarter of 2018.


  1. Solosec Prescribing Information. Symbiomix Therapeutics. September 2017.
  2. Centers for Disease Control and Prevention. 2015 Sexually Transmitted Diseases Treatment Guidelines. Bacterial Vaginosis. Available at: Accessed Oct. 23, 2017.
  3. Schwebke JR, Morgan FG Jr, Koltun W, Nyirjesy P. A phase-3, double-blind, placebo-controlled study of the effectiveness and safety of single oral doses of secnidazole 2 g for the treatment of women with bacterial vaginosis. Am J Obstet Gynecol 2017; Sep 1. pii: S0002-9378(17)30964-X. doi: 10.1016/j.ajog.2017.08.017. [Epub ahead of print].
  4. U.S. Department of Health and Human Services. Food and Drug Administration. Center for Drug Evaluation and Research. Bacterial Vaginosis: Developing Drugs for Treatment, Guidance for Industry. Available at: Accessed Oct. 23, 2017.