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Metronidazole

Antibiotic

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What is metronidazole?

Metronidazole (also called Flagyl®) is a medicine used to treat infections. Metronidazole is available in these forms taken by mouth:

  • a 250-mg round, white tablet
  • a 50 mg/ml pink liquid suspension

Metronidazole is also available as a clear liquid given by vein.

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Possible side effects

  • Nausea, vomiting
  • Loss of appetite
  • Metallic taste
  • Headache
  • Diarrhea
  • Feeling dizzy

Tell your doctor right away if you have any of the following side effects:

  • Skin rash, hives, itching
  • Trouble breathing or swallowing
  • Unexplained sore throat or fever
  • Joint pain
  • Tingling, pain, or weakness in the hands or feet
  • These are the most common side effects, but there may be others. Please report all side effects to the doctor or nurse.

Symptoms of an allergic reaction include: rash, hives, itching, chills, fever, headache, muscle ache, shortness of breath, coughing, tightness in the throat, swelling of the face or neck.

Not all patients who take metronidazole will experience these side effects. Common side effects are bolded, but there may be others. Please report all suspected side effects to your doctor or pharmacist.

Find more information on side effects.

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Tips for patients and families

Be sure to discuss all questions and instructions with your doctor or pharmacist. 

  • Take all doses of this medicine, even if you begin to feel better before all doses are taken.
  • You should not consume any alcohol during metronidazole therapy and for one (1) day afterward. Alcohol is found in most over-the-counter cough and cold medicines.
  • Let your doctor know if you have had seizures or if you have numbness or tingling in your hands or feet.
  • Let your doctor or dentist know you are taking metronidazole before you have surgery requiring general anesthesia.
  • Metronidazole may turn your urine a reddish-brown color. This is normal.
  • This medicine may cause you to feel dizzy. Be careful when driving or using machinery.
  • Metronidazole may affect the way other medicines work, and other medicines can affect the way metronidazole works. These include:
    • Warfarin (Coumadin®)
    • Phenytoin (Dilantin®)
    • Phenobarbital
    • Cimetidine (Tagamet®)
    • Medicines containing alcohol.
  • Always tell your doctor if you are taking these medicines or if you start taking any new medicine while taking metronidazole.

Metronidazole at home:

  • Take this medicine with or without food. If you have stomach upset, take metronidazole with food.
  • Shake the liquid suspension well before you take it. Use a medicine cup or an oral syringe to measure your dose to make sure you are taking the correct amount.
  • Store the liquid suspension in the refrigerator.
  • Store metronidazole tablets at room temperature in a dry place.
  • Discard the liquid suspension after 30 days or when the date on the label expires.
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Always check the medication label. Many medicines look the same. Do not take any new medicine, including over-the counter medicines or supplements, without checking with your doctor or pharmacist. Talk to your doctor or pharmacist about what to do in the case of a missed dose, allergic reaction, or medical emergency. 

This information is not intended to be a complete guide and is not a substitute for talking with your provider. Medicine names, appearance, formulas, or availability may vary by clinic location. Always follow the instructions given by your care team.

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Reviewed: June 2024