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Generic Name: metronidazole (MET-roe-NID-a-zole)
Brand Name: Flagyl

Long-term use of Flagyl has caused cancer in mice and rats. Discuss any questions or concerns with your doctor. Do not use Flagyl for a condition other than the one for which it was prescribed.


Flagyl is used for:

Treating certain infections caused by bacteria or amoebas. It may also be used for other conditions as determined by your doctor.

Flagyl is an oral antiprotozoal and antibacterial. It is thought to work by entering the bacterial cell, acting on some components of the cell, and destroying the bacteria.

Do NOT use Flagyl if:

  • you are allergic to any ingredient in Flagyl or to another nitroimidazole (eg, tinidazole)
  • you are in the first 3 months of pregnancy
  • you are taking busulfan or you have taken disulfiram within the past 2 weeks
  • you drink alcohol or take any products containing alcohol or propylene glycol. Check with your doctor or pharmacist if you are unsure if any of your medicines contain alcohol or propylene glycol

Contact your doctor or health care provider right away if any of these apply to you.

Before using Flagyl:

Some medical conditions may interact with Flagyl. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines, foods, or other substances
  • if you have a history of nerve, brain, or blood problems; Crohn disease; liver or kidney problems; or seizures

Some MEDICINES MAY INTERACT with Flagyl. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Disulfiram because side effects, such as mental or mood changes, may occur
  • Cimetidine because it may increase the risk of Flagyl's side effects
  • Barbiturates (eg, phenobarbital) or phenytoin because they may decrease Flagyl's effectiveness
  • Anticoagulants (eg, warfarin), busulfan, or lithium because the risk of their side effects may be increased by Flagyl

This may not be a complete list of all interactions that may occur. Ask your health care provider if Flagyl may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Flagyl:

Use Flagyl as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Take Flagyl by mouth with or without food.
  • To clear up your infection completely, take Flagyl for the full course of treatment. Keep taking it even if you feel better in a few days.
  • If you miss a dose of Flagyl, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Ask your health care provider any questions you may have about how to use Flagyl.

Important safety information:

  • Flagyl may cause dizziness. This effect may be worse if you take it with alcohol or certain medicines. Use Flagyl with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
  • Do not drink alcohol or take any products containing alcohol or propylene glycol while you are taking Flagyl and for at least 3 days after the last dose. Drinking alcohol or taking products with alcohol or propylene glycol may cause stomach cramps, nausea, vomiting, headaches, and flushing.
  • Flagyl only works against bacteria; it does not treat viral infections (eg, the common cold).
  • Be sure to use Flagyl for the full course of treatment. If you do not, the medicine may not clear up your infection completely. The bacteria could also become less sensitive to this or other medicines. This could make the infection harder to treat in the future.
  • Long-term or repeated use of Flagyl may cause a second infection. Tell your doctor if signs of a second infection occur. Your medicine may need to be changed to treat this.
  • Some patients have developed persistent nerve problems (peripheral neuropathy) after taking Flagyl for a long period of time. Tell your doctor right away if you develop signs of nerve problems (eg, numbness; tingling; burning of the arms, hands, legs, feet). Do NOT take more than the recommended dose or use for longer than prescribed without checking with your doctor.
  • Flagyl may interfere with certain lab tests. Be sure your doctor and lab personnel know you are taking Flagyl.
  • Lab tests, including liver function and white blood cell counts, may be performed while you use Flagyl. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use Flagyl with caution in the ELDERLY; they may be more sensitive to its effects.
  • Flagyl should be used with extreme caution in CHILDREN; safety and effectiveness in children have not been confirmed.
  • PREGNANCY and BREAST-FEEDING: If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of taking Flagyl while you are pregnant. Certain patients should not use Flagyl during the first 3 months of pregnancy. Discuss any questions with your doctor. Flagyl is found in breast milk. Do not breast-feed while taking Flagyl.

Possible side effects of Flagyl:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Appetite loss; constipation; diarrhea; dizziness; headache; metallic taste; nausea; stomach upset or cramping; trouble sleeping; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bloody stools; confusion; decreased coordination; depression; fainting; increased or decreased urination; irritability; numbness, tingling, or burning of the arms, hands, legs, or feet; red, swollen, blistered, or peeling skin; seizures; severe diarrhea; severe or persistent dizziness or headache; severe or persistent stomach pain or cramping; sore throat, chills, or fever; speech problems; stiff neck; vaginal itching, odor, or discharge; vision loss or other vision changes; weakness; white patches in the mouth.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately.

Proper storage of Flagyl:

Store Flagyl at room temperature, between 68 and 77 degrees F (20 and 25 degrees C). Store away from heat, moisture, and light. Do not store in the bathroom. Keep Flagyl out of the reach of children and away from pets.

General information:

  • If you have any questions about Flagyl, please talk with your doctor, pharmacist, or other health care provider.
  • Flagyl is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information should not be used to decide whether or not to take Flagyl or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about Flagyl. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to Flagyl. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using Flagyl.

Issue Date: April 2, 2014
Database Edition 14.2.1.001
Copyright © 2014 Wolters Kluwer Health, Inc.

Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.

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