What You Need To Know About Flagyl (Metronidazole)

Flagyl Is An Antibiotic That Is Used To Treat Infections

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Generic name: Metronidazole
Other brand name: Protostat

What Is It?

Flagyl (metronidazole) is an antibacterial drug that is classified as a broad-spectrum antibiotic. It is used to kill any bacteria in the body that are causing infection. In some cases, Flagyl may be used to treat infections or other complications of IBD. It might be given alternately or at the same time as ciprofloxacin, another type of antibiotic.

How Is It Taken?

When taken at home to treat an infection, Flagyl is taken orally in tablet form. In order for Flagyl to effectively kill harmful bacteria, it is important to maintain a constant level of the drug in the blood. Therefore, it must be taken at regular intervals without missing any doses. Take Flagyl with 8 ounces of water.

Flagyl can be taken by itself, or it can be taken with meals. If dry mouth becomes bothersome, try chewing gum, or sucking on hard candy or ice chips.

Why Is It Prescribed?

Flagyl is used to fight off, or to prevent, a bacterial infection. It is used to treat a wide variety of infections, including those in the abdomen, bones, joints, nervous system, respiratory tract, and skin, as well as vaginal and intestinal infections.

If You Miss a Dose

If you miss a dose, take it as soon as you remember. If your next dose should be taken soon, just take that dose. Don't double up or take more than one dose of Flagyl at a time.

Who Should Not Take It? 

People with an allergy or sensitivity to metronidazole should also not take Flagyl. Flagyl should be used under the close supervision of a physician by anyone who has liver disease.

Yeast infections may worsen while taking Flagyl.

Can I Stop Taking It Early?

NO. As you are treated with Flagyl, you may start to feel better, but that does not mean the infection is entirely gone.

Take all of the medication that was prescribed to you unless instructed to stop taking it by a healthcare professional. Stopping the medication before the bacterial infection is completely gone can result in serious consequences. A stronger strain of bacteria may develop, or the infection may come back again and be more difficult to treat.

Side Effects

The most serious side effects from Flagyl are seizures and tingling or numbness in the extremities (arms, legs, hands, and feet). If you experience these symptoms, stop taking Flagyl and call your doctor immediately.

Other side effects include abdominal cramping, diarrhea, headache, nausea, loss of appetite, and vomiting. See the Flagyl side effects page for a complete list.

Medication Interactions

Flagyl could interact with several drugs. Tell the prescribing physician about all drugs and nutritional supplements you are currently taking, especially those from the following list, which may interact with Flagyl.

  • Alcohol
  • Amprenavir
  • Anticoagulants (such as Warfarin)
  • Barbiturate medicines for inducing sleep or treating seizures (convulsions)
  • Carbamazepine
  • Cimetidine
  • Disulfiram (Antabuse)
  • Dofetilide
  • Fluorouracil
  • Lithium
  • Methadone
  • Phenytoin
  • Sirolimus
  • Tacrolimus

    Food Interactions

    Alcoholic beverages should not be consumed until 72 hours (3 days) after the last dose of Flagyl is taken. Consuming alcohol while taking Flagyl could result in abdominal cramps, nausea, vomiting, headaches, and flushing. Flagyl can also change the taste of alcohol. Take care to avoid alcohol from unexpected sources, such as over-the-counter cough suppressants or cold products (NyQuil, for example).

    Safe During Pregnancy?

    Pregnant women in their first trimester should avoid Flagyl.

    The FDA has classified Flagyl as a type B drug. The effect that Flagyl has on an unborn child has not been studied extensively.

    Flagyl should only be used during pregnancy if it is clearly needed. Notify the prescribing doctor if you become pregnant while you are taking Flagyl. Flagyl does pass into breast milk and could affect a nursing infant. It should be used with care in nursing mothers.

    Combine It With Milk Thistle?

    Milk thistle (Silybum marianum) may help to protect the liver from medications that may harm it, such as Flagyl. It has not been studied in direct correlation with Flagyl, but it may be prescribed as a complementary therapy.

    Will It Worsen IBD Diarrhea?

    Antibiotics kill off bacteria in the body, and many can't distinguish between "good" and "bad" bacteria. Therefore, with some antibiotics, "good" bacteria in the colon may be killed along with the "bad," resulting in diarrhea. However, Flagyl doesn't tend to cause antibiotic-associated diarrhea—in fact, it may be a treatment for it.

    A Word From Verywell

    Flagyl is a common antibiotic that is used to treat a variety of conditions. Some people do experience side effects, but they are often manageable. For side effects that become troublesome or can't be managed, a doctor should be contacted right away.


    Pfizer. "FLAGYL U.S. Physician Prescribing Information." Pfizer Inc. Apr 2010. 24 Jan 2012.

    The American Society of Health-System Pharmacists, Inc. "Metronidazole Oral." MedLine Plus 1 Sept 2008. 24 Jan 2012.