Using Metronidazole to Treat Bacterial Vaginosis

Bacterial vaginosis (BV) is a common bacterial vaginal infection affecting roughly 30% of women ages 14 to 49 in the United States. This infection occurs when bad bacteria outweigh good bacteria in the vagina. 

84% of women with BV do not have symptoms. When symptoms are present, the most common is a strong “fishy” vaginal odor and an increase in vaginal discharge.

Metronidazole (such as the brand Flagyl) is an antibiotic used to treat bacterial vaginosis. This article reviews the basics of metronidazole, dosage, side effects, effectiveness, other medications for BV, and more. 

Metronidazole for Bacterial Vaginosis

Metronidazole is considered the first line of treatment for BV. This means it’s one of the preferred antibiotics used to treat BV. 

Metronidazole is the generic version. Brand names include: 

• Flagyl
• Protostat
• MetroCream 
• MetroGel 
• Noritate
• Vandazole
• Nuvessa
• Pylera

Metronidazole comes in capsules, tablets (pills), creams, gels, and intravenous (IV) forms. It can be given orally (by mouth), vaginally, or intravenously. Prescriptions to treat BV are typically for oral or vaginal administration. 

Dosage

The following are typical dosages for metronidazole when treating BV:

• Oral dose: 500 milligrams (mg) twice daily for seven days
• Intravaginal dose: 0.75% gel, one applicator intravaginally for five nights

Sometimes, healthcare providers will prescribe oral and vaginal medications for you to take simultaneously. They might also increase the dose or time you take the medication, especially if the infection returns after initial treatment.

Side Effects

Common side effects of metronidazole include:

• Nausea and vomiting
• Abdominal pain
• Metallic taste

Less common side effects include:

• Central nervous system issues, such as seizures
• Yeast infections
• Rash or itching
• Thrombocytopenia (low platelet count)
• Heart rhythm changes
• Kidney problems

Interactions

Metronidazole can interact with the following medications:

• Coumadin, Jantoven (warfarin)
• Lithobid, Eskalith (lithium)
• Clindacin, Cleocin, Clindesse (clindamycin)
• Some anti-seizure medications

Vaginal metronidazole can increase your chance of getting a yeast infection. Your provider may prescribe Diflucan (fluconazole) by mouth or probiotics to decrease this risk, especially with extended treatment. 

Metronidazole vaginal cream can weaken birth control methods such as latex condoms and diaphragms. It’s best to use another form of birth control during treatment and for five days after treatment is complete.

Effectiveness

Some studies show a cure rate of over 90% after one week of treatment and 70% to 80% after four weeks.

There is some concern that metronidazole alone may temporarily balance the bacteria in the vagina, but the risk of recurrence is high. Adding probiotics along with antibiotics is becoming a more common practice. Probiotics can help with a more permanent or long-term solution to balancing the vaginal flora (microorganisms).

Other Bacterial Vaginosis Medications

One of the following antibiotics may also be used to treat BV: 

• Clindam, Cleocin, Clindesse (clindamycin): 300 mg twice daily for seven days, taken orally
• Clindam, Cleocin, Clindesse (clindamycin): 100 mg each night for three nights, intravaginally
• Tindamax, Fasigyn, Simplotan (tinidazole): 2 grams per day for two days or 1 gram per day for five days, taken orally
• Solosec (secnidazole): 2 grams in a single dose, taken orally

While not as common, Xifaxan (rifaximin) may also be prescribed for BV. 

Alternative Treatment Options

Your healthcare provider may also consider the following alternative treatments, either alone or with antibiotic treatment:

• Probiotics (oral or vaginal)
• Boric acid 
• Vaginal vitamin C
• Sucrose gel

Recurrence 

Recurring (returning) infections are common after treatment of BV. In fact, 50% of women get another infection within 12 months of treatment. BV is considered recurring when a woman has at least three infections in one year. 

If you have a recurring infection, your healthcare provider may increase the dose and time you take antibiotics. Sometimes, they prescribe a maintenance dose of vaginal cream to help prevent a recurrence.

It’s best to avoid sexual contact until treatment has ended and your symptoms have resolved. If your intimate partner is a woman, they should seek treatment as BV can spread between female sex partners. However, if your intimate partner is male, research does not indicate that they need treatment.

Summary 

Bacterial vaginosis (BV) is a common bacterial vaginal infection that occurs when bad bacteria outweigh good bacteria in the vagina. Metronidazole is an antibiotic used to treat BV. It can be given orally (by mouth) or intravaginally (inserted into the vagina). The most common side effects are stomach upset. 

Metronidazole is highly effective, but the chances of the infection recurring are high. In this case, healthcare providers may prescribe higher doses for longer, both vaginal and oral medication together, and probiotics to prevent a recurrence. 

Alternative antibiotics and other treatments, such as boric acid, vaginal vitamin C, or sucrose gel, may also be suggested. 

A Word From Verywell

Having bacterial vaginosis can be inconvenient, frustrating, and embarrassing. It can occur and reoccur even when you have been trying your best to prevent it. Finish the entire metronidazole prescription for BV. Not taking all of it can increase your chance of recurrence or resistance to the antibiotic.