OverviewDosageSide EffectsInteractionsHalf-Life

Generic Name: Metronidazole
Brands: Metrogel, MetroCream, Noritate, Nuvessa, MetroLotion, Flagyl, Metro I.V.
Class: Antibiotic
Availability: Prescription needed
Molecular Formula: C6H9N3O3
Substance UNII: 140QMO216E

What is Metronidazole?

Metronidazole is an antibiotic. It is often sold under the brand names Metrogel, MetroCream, Noritate, Nuvessa, MetroLotion, Flagyl, and Metro I.V. It comes in a variety of formulations, including capsule, cream, tablet, and suppository. It is available in regular and extended release versions, the latter of which provides longer-lasting treatment.

What is Metronidazole Used For?

Metronidazole treats or prevents certain types of bacterial infections, specifically those affecting the vagina, gastrointestinal (GI) tract, skin, heart, bones, joints, lungs, blood, nervous system, and other areas of the body. Metronidazole is especially beneficial in the treatment of infections caused by protozoa, which are single-cell parasites that feed on other organisms, organic tissue, and debris.

Various formulations of metronidazole treat specific conditions. Dermatologists sometimes prescribe the topical formula of metronidazole to treat skin redness and pimples associated with the skin condition rosacea, for example.

Doctors may also prescribe vaginal metronidazole gel to treat bacterial infections of the vagina; note that metronidazole will not treat a vaginal yeast infection. Physicians might also prescribe metronidazole to treat the common sexually transmitted infection, or STI (formerly known as sexually transmitted disease, or STD), trichomoniasis.

How Does Metronidazole Work?

Metronidazole works by stopping the growth of bacteria, according to the National Library of Medicine. Metronidazole has to get inside of the bacteria to stop the production of proteins. Specifically, it interacts with the bacteria’s DNA in ways that weaken the DNA structure, which in turn weakens the bacteria by stopping the bacteria from using DNA to make proteins.  

How Long Does it Take for Metronidazole to Work?

The length of time it takes for metronidazole to work depends on a number of factors, including the formulation or strength of the medication. In the treatment of most infections, though, it starts to work in a few days. The cream or gel formulation, however, may take a few weeks to see results.

Do Not Use Metronidazole If:

There are several situations where this medication may not be the right choice. According to the U.S. National Library of Medicine (NLM), the following should not use metronidazole:

  • Those who are hypersensitive to the effects of metronidazole or any of its components
  • Those with trichomoniasis who are in the first trimester of pregnancy
  • Additionally, do not take with alcohol or within a few days of taking metronidazole. If you are taking warfarin (jantoven) be sure to let your doctor know since they may alter the dose of warfarin

Please note that this list may be incomplete as there may be other situations where metronidazole use is not advisable.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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