The most common medicine used for bacterial vaginosis (BV) is metronidazole, an antibiotic available as both an oral pill and a vaginal gel. Clindamycin, another antibiotic, serves as an equally effective alternative. Both are considered first-line treatments, and your provider will typically choose between them based on your preferences and medical history.
Metronidazole: The Most Prescribed Option
Metronidazole is the go-to antibiotic for BV. It works by entering the harmful bacteria that overgrow during an infection and damaging their DNA from the inside, which kills them. What makes it especially useful for BV is that it selectively targets the oxygen-avoiding bacteria responsible for the infection while leaving healthy cells largely alone. Bacteria that thrive in oxygen-rich environments can’t activate the drug, so it zeroes in on exactly the type causing your symptoms.
The standard oral regimen is 500 mg taken twice a day for seven days. If you’d rather avoid pills, a vaginal gel version (0.75%) is applied once daily for five days using a prefilled applicator. Both forms are effective, but the gel tends to cause fewer digestive side effects like nausea. The oral version, on the other hand, is simpler for some people since there’s no applicator involved.
One important rule with metronidazole: avoid alcohol completely while taking it and for at least two days after finishing. Mixing the two can cause intense nausea, vomiting, cramping, and flushing. This applies to the oral tablets, liquid forms, and suppositories.
Clindamycin as an Alternative
Clindamycin works differently from metronidazole but is just as effective. It’s available as a vaginal cream applied at bedtime for seven days, or as oral capsules. Some providers also prescribe vaginal suppositories (ovules) that require only a three-day course.
One thing to be aware of: clindamycin cream is oil-based, which means it can weaken latex condoms and diaphragms. If you rely on these for contraception or protection, you’ll need a backup method during treatment and for a few days afterward. This doesn’t apply to the oral capsule form.
Single-Dose Treatment With Secnidazole
For people who struggle to complete a week-long course of antibiotics, secnidazole offers a one-and-done option. It’s a single 2-gram packet of granules taken just once. You sprinkle the entire packet onto soft food like applesauce, yogurt, or pudding and eat the whole mixture within 30 minutes. The granules don’t dissolve and shouldn’t be chewed or crunched. A glass of water afterward helps wash everything down.
Secnidazole belongs to the same drug family as metronidazole, so it kills bacteria through the same DNA-disrupting mechanism. The convenience factor is its biggest advantage. The downside is cost: as a newer, brand-name medication, it’s often significantly more expensive than generic metronidazole, and not all insurance plans cover it.
Tinidazole: Another Oral Option
Tinidazole is closely related to metronidazole and works the same way. It’s typically prescribed as an oral tablet taken once daily for a shorter course, usually two to five days depending on the dose. Providers often turn to tinidazole when metronidazole causes too many side effects or when an initial round of treatment doesn’t clear the infection. Like metronidazole, you need to avoid alcohol during treatment and for several days after.
Why BV Often Comes Back
Antibiotics clear BV effectively in the short term, with most people seeing symptoms resolve within a week. The frustrating reality, though, is that BV has one of the highest recurrence rates of any vaginal infection. Roughly half of those treated will have another episode within six to twelve months. This isn’t because the antibiotics failed. It’s because BV is fundamentally a disruption in the vaginal microbiome, and antibiotics kill the overgrown harmful bacteria without necessarily restoring the protective bacteria that keep the environment balanced.
For recurrent BV (three or more episodes in a year), providers sometimes recommend a longer course of treatment or a suppressive regimen where you use vaginal metronidazole gel periodically over several months to keep symptoms from returning.
Probiotics for Prevention
There’s growing interest in using probiotics alongside antibiotics to help rebuild the vaginal microbiome after treatment. A clinical trial published by researchers and reported by Harvard Health found that women who used a vaginal probiotic containing Lactobacillus crispatus (a key species in a healthy vaginal environment) twice weekly for 11 weeks after standard antibiotic treatment had notably fewer recurrences. Only 30% of the probiotic group saw BV return by week 12, compared with 45% of those who used a placebo.
Oral probiotic supplements marketed for vaginal health are widely available, but the evidence is strongest for probiotics applied directly to the vagina. Over-the-counter vaginal probiotic suppositories exist, though they vary in quality and strain composition. If you’re dealing with recurring BV, it’s worth discussing targeted probiotic use with your provider.
Treatment During Pregnancy
BV during pregnancy is treated with the same antibiotics, primarily oral metronidazole. Treating BV in pregnancy matters because untreated infections are associated with preterm birth and low birth weight. The oral form is generally preferred over vaginal gels during pregnancy so the medication reaches the entire reproductive tract. Both metronidazole and clindamycin have long safety records in pregnant patients, including during the first trimester.
What to Expect During Treatment
Most people notice improvement within two to three days of starting antibiotics, particularly the characteristic fishy odor and grayish discharge. Even if symptoms clear quickly, finishing the full course matters. Stopping early allows surviving bacteria to repopulate and increases the chance of recurrence.
Common side effects with oral metronidazole include nausea, a metallic taste in the mouth, and mild stomach upset. Taking it with food helps. Vaginal treatments can sometimes cause local irritation or a yeast infection, since killing off one type of bacteria can allow yeast to overgrow in the newly open space. If you develop itching, thick white discharge, or burning after finishing BV treatment, a secondary yeast infection is the likely culprit and is easily treated with an antifungal.