Oral or topical metronidazole for bacterial vaginosis is effective. Bacterial vaginosis is a vaginal infection seen frequently in women and is normally caused by overgrowth of an anaerobic organism, Gardnerella vaginalis. The use of metronidazole, both topically and orally, has shown good results in eradicating the condition.

The bacterial flora in the vagina is a finely maintained balance of anaerobic and Lactobacillus bacteria. The exact cause of bacterial vaginosis is not established, but it seems that numerous factors can affect the fine balance of bacterial growth. It is thought that some practices may increase a woman's risk of having bacterial vaginosis. These include douching and unprotected sexual intercourse. It does not, however, only occur in sexually active women and recurrence is common, causing some medical practitioners to treat sexual partners, although this is controversial.

While bacterial vaginosis may be asymptomatic and, in these cases, probably doesn't need treatment, it usually presents with vaginal discharge, a "fishy" odor and pain during intercourse. Should these symptoms occur, medical help should be sought. Bacterial vaginosis usually doesn't have any complications but may increase a women's risk of getting a sexually transmitted disease (STD) and, in pregnant women, may increase the risk of premature labor, so treatment is essential.

Metronidazole for bacterial vaginosis is the most well-recognized treatment. It is known by different trade names in different countries, by manufacturer, and is usually available by prescription only. It is important that the prescribed dose is taken and the full course is completed, even if symptoms subside. Stopping using metronidazole for bacterial vaginosis before the course is finished may increase the chances of recurrence and make treatment of that recurrence more difficult.

The usual dose of oral metronidazole for bacterial vaginosis is a daily or twice daily dose for seven days. If used topically, metronidazole is inserted intra-vaginally at bedtime every night for five nights. It is important that pregnancy, desired pregnancy and lactation are discussed with the prescribing doctor before beginning treatment with metronidazole for bacterial vaginosis.

As with any medication, metronidazole may interact with other medications and these, including over-the-counter, homeopathic and complementary medicines, should be discussed with the prescribing doctor. Alcohol should be avoided completely while taking metronidazole, as it may cause a disulfiram-like reaction which can cause flushing, abdominal cramps and severe nausea and vomiting. Adverse effects which may occur include gastrointestinal effects such as diarrhea, nausea and vomiting, or headache. Should any side effect be severe, medical attention should be sought.