How are antibiotics used?

The symptoms of bacterial vaginosis are usually treated with antibiotics such as clindamycin or metronidazole – in the form of a cream, vaginal suppositories or tablets, or oral tablets (to be swallowed). The treatment can last one to seven days depending on the exact drug used, its form, the dose, and the severity of the symptoms. You can talk to your doctor about what type of treatment is most suitable for you.

If you've been prescribed antibiotics, it's important to make sure you use them correctly. That especially means using the medicine regularly and for as long as prescribed: If you stop early – for instance, because the symptoms have already cleared up – resistant strains of bacteria are more likely to develop.

How effective are antibiotics?

Clindamycin and metronidazole are very effective against vaginosis symptoms. Research on treatment with clindamycin creams has shown the following:

• Without clindamycin: 50% of the study participants who used a placebo (fake treatment) had no symptoms one to two weeks afterwards.
• With clindamycin: 88% of the study participants who used clindamycin had no symptoms one to two weeks after treatment.

Several studies have also shown that clindamycin and metronidazole are similarly effective: In the studies comparing these two antibiotics, over 90% of the women had no symptoms after treatment – regardless of which drug they had used.

Bacterial vaginosis can come back after a few weeks. That happens quite often: About half of all women have symptoms again about one year after the first infection. If you keep getting bacterial vaginosis, it may be a good idea to discuss the prevention options with your doctor.

Researchers have also looked into whether it's a good idea for your partner to take antibiotics too. But that wasn’t shown to speed up the recovery time or prevent the infection from coming back.

What are the side effects?

The antibiotics don’t only kill gardnerella bacteria. They also kill useful bacteria in the vagina that help to keep other germs in check. This means that treatment with antibiotics can sometimes end up causing a vaginal yeast infection (thrush). This happens in about 10% of women who use clindamycin or metronidazole. The typical symptoms of vaginal thrush include itching and a thick, white discharge. They can also be treated with medication.

Antibiotics occasionally have other side effects too. About 10% of women who take metronidazole tablets say that the tablets leave a metallic taste in their mouth. Less commonly, they cause nausea and vomiting. Clindamycin is very well tolerated when used as a cream, and has no known side effects apart from yeast infections (thrush).

Can lactic acid bacteria help?

Lactic acid bacteria are believed to help restore a healthy balance of germs in the vagina (healthy vaginal flora) and keep harmful bacteria in check. But there is less research on treatment with lactic acid bacteria than on treatment with antibiotics. Very few studies have looked at treatments with lactic acid bacteria on their own – they were usually used in combination with antibiotics. But there is currently no scientific proof that vaginosis clears up any better when using this combination. Little is known about the possible side effects of these medications.

Can vaginosis be treated during pregnancy?

If bacterial vaginosis develops during pregnancy, it can slightly increase the risk of the baby being born too early (preterm birth). There is also a higher risk of a late-term miscarriage or stillbirth (between week 13 and week 24 of pregnancy).

Researchers from the Cochrane Collaboration analyzed the results of studies on the advantages and disadvantages of antibiotics. They included a total of 21 studies involving nearly 8,000 pregnant women. They concluded that antibiotics can lower the risk of late-term miscarriages:

• 2% of women who didn't take antibiotics had a late-term miscarriage.
• 0.3% of women who took antibiotics had a late-term miscarriage.

Antibiotics had no influence on the risk of preterm birth or the risk of the woman’s waters breaking too soon (premature rupture of membranes). About 2% of the women stopped the treatment due to side effects. There is no evidence that the antibiotics have any long-term side effects or harm the child when used to treat bacterial vaginosis.

Most of the study participants had no symptoms. Their infection was detected during other routine pregnancy tests. If bacterial vaginosis starts causing symptoms during pregnancy, it is usually treated.

Sources

• Amaya-Guio J, Viveros-Carreno DA, Sierra-Barrios EM et al. Antibiotic treatment for the sexual partners of women with bacterial vaginosis. Cochrane Database Syst Rev 2016; (10): CD011701. [PMC free article: PMC6458027] [PubMed: 27696372]
• Brocklehurst P, Gordon A, Heatley E et al. Antibiotics for treating bacterial vaginosis in pregnancy. Cochrane Database Syst Rev 2013; (1): CD000262. [PMC free article: PMC11307253] [PubMed: 23440777]
• Huang H, Song L, Zhao W. Effects of probiotics for the treatment of bacterial vaginosis in adult women: a meta-analysis of randomized clinical trials. Arch Gynecol Obstet 2014; 289(6): 1225-1234. [PubMed: 24318276]
• Li C, Wang T, Li Y et al. Probiotics for the treatment of women with bacterial vaginosis: A systematic review and meta-analysis of randomized clinical trials. Eur J Pharmacol 2019; 864: 172660. [PubMed: 31562865]
• Oduyebo OO, Anorlu RI, Ogunsola FT. The effects of antimicrobial therapy on bacterial vaginosis in non-pregnant women. Cochrane Database Syst Rev 2009; (3): CD006055. [PubMed: 19588379]
• Tan H, Fu Y, Yang C et al. Effects of metronidazole combined probiotics over metronidazole alone for the treatment of bacterial vaginosis: a meta-analysis of randomized clinical trials. Arch Gynecol Obstet 2017; 295(6): 1331-1339. [PubMed: 28386675]

• IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

  Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

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