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What Is Metronidazole?

Metronidazole is an antibiotic that is used to treat a wide variety of infections. It works by stopping the growth of certain bacteria and parasites. This antibiotic treats only certain bacterial and parasitic infections. It will not work for viral infections. Using any antibiotic when it is not needed can cause it to not work for future infections. Metronidazole may also be used with other medications to treat certain stomach/intestinal ulcers caused by a bacteria (H. pylori).

Uses and how it Works

Metronidazole immediate-release oral tablets are used to treat many infections caused by bacteria or parasites. These include infections that occur in the gastrointestinal tract or reproductive system such as amebiasis and trichomoniasis. Metronidazole extended-release oral tablets are used to treat vaginal infections in women as well. Also, Metronidazole may be used as part of a combination therapy. This means you may need to take it with other medications.

Metronidazole belongs to a class of drugs called nitroimidazole antimicrobials. This class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions. Nitroimidazole antimicrobials treat infections caused by bacteria and other organisms called protozoa. Metronidazole tablets work by killing the bacteria or other organism that’s causing the infection.

Before taking this medicine

You should not take metronidazole if you are allergic to it, or if you have taken disulfiram within the past 2 weeks. Using metronidazole during pregnancy could harm the unborn baby. Make sure to tell your doctor if you are pregnant or if you become pregnant while using this medicine. To make sure metronidazole is safe for you, tell your doctor if you have ever had:

  • liver or kidney disease;
  • Cockayne syndrome;
  • a stomach or intestinal disease such as Crohn's disease;
  • a blood cell disorder such as anemia or low white blood cell (WBC) counts;
  • a fungal infection anywhere in your body; or
  • a nerve disorder.

Metronidazole Side Effects

Common Side Effects of Metronidazole

Tell your doctor if any of the following side effects become severe or don't go away:

  • Vomiting
  • Mild diarrhea
  • Upset stomach
  • Cough, sneezing, or runny nose
  • Dark or reddish-brown urine
  • Mouth or tongue irritation

Serious Side Effects of Metronidazole

Tell your doctor immediately if you experience any of the following serious side effects:

  • Numbness or tingling in the hands or feet
  • White patches or sores in the mouth
  • Painful urination
  • Vision problems or pain behind the eyes
  • Trouble concentrating
  • Mood or behavior changes
  • Tremors
  • Seizures

How should I take metronidazole?

You should always take metronidazole exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, you can always ask your pharmacist for one.

Do not crush, chew, or break an extended-release tablet. Swallow it whole. If you are treating a vaginal infection, your sexual partner may also need to take metronidazole or you could become infected again. Metronidazole is usually given for up to 10 days in a row. You may need to repeat this dosage several weeks later.

If you miss a dose of metronidazole, take it as soon as you remember. But skip the missed dose if it's almost time for your next scheduled dose. Don't take extra medicine to make up for a missed dose.