Metronidazole is a medicine used to treat different types of bacterial and parasitic infections, including those that affect the skin, vagina, blood, heart, bone, stomach, liver, joints, nervous system, respiratory tract, and other areas of the body.

This medicine is also prescribed to treat sexually transmitted diseases (STDs). The extended-release form of metronidazole is used to treat bacterial vaginosis (an infection caused by too much harmful bacteria in the vagina) in women.

Metronidazole is in a class of drugs called nitroimidazole antimicrobials. It works by stopping the growth of bacteria.

This medicine will only help infections caused by bacteria and will not work for the common cold, flu, or other viral infections.

uses

What is Metronidazole (Flagyl) used for?

Amebiasis
Bacterial Vaginosis
Balantidium coli
Dientamoeba fragilis
Giardiasis
Helicobacter pylori Infection
Intraabdominal Infection
Joint Infection
Nongonococcal Urethritis
Osteomyelitis
Pelvic Inflammatory Disease
Peritonitis
Pseudomembranous Colitis
Skin or Soft Tissue Infection
Trichomoniasis
Bacterial Infection
Skin and Structure Infection
Surgical Prophylaxis
Liver Abscess
STD Prophylaxis
Wound Infection

warnings

What is the most important information I should know about Metronidazole (Flagyl)?

You should not use this medicine if you are allergic to metronidazole, secnidazole, or tinidazole, or if:

you drank alcohol in the past 3 days;
you consumed foods or medicines that contain propylene glycol in the past 3 days; or
you took disulfiram (Antabuse) within the past 14 days.

May harm an unborn baby. Do not use metronidazole to treat trichomoniasis during the first trimester of pregnancy. Tell your doctor if you become pregnant.

Not all uses of metronidazole are approved for treating children and teenagers. Metronidazole is not approved to treat vaginal infections in girls who have not begun having menstrual periods.

Tell your doctor if you have ever had:

liver disease;
kidney disease (or if you are on dialysis);
a heart rhythm disorder;
a stomach or intestinal disease such as Crohn's disease;
a blood cell disorder such as anemia (lack of red blood cells) or low white blood cell (WBC) counts;
a fungal infection anywhere in your body; or
a nerve disorder.

Metronidazole has caused cancer in animal studies. However, it is not known whether this would occur in humans. Ask your doctor about your risk.

You should not breastfeed within 24 hours after using metronidazole. If you use a breast pump during this time, throw out the milk and do not feed it to your baby.

Side Effects

What are the side effects of Metronidazole (Flagyl)?

Get emergency medical help if you have signs of an allergic reaction (hives, itching, warmth or tingling; fever, joint pain; dry mouth, dry vagina; stuffy nose, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Call your doctor at once if you have:

new or worsening symptoms of infection;
painful or difficult urination;
confusion;
a light-headed feeling (like you might pass out);
vaginal itching or discharge; or
blisters or ulcers in your mouth, red or swollen gums, trouble swallowing.

Stop taking the medicine and call your doctor right away if you have neurologic side effects (more likely to occur while taking metronidazole long term):

numbness, tingling, or burning pain in your hands or feet;
vision problems, pain behind your eyes, seeing flashes of light;
muscle weakness, problems with speech or coordination;
trouble speaking or understanding what is said to you;
a seizure; or
fever, neck stiffness, and increased sensitivity to light.

Metronidazole can cause life-threatening liver problems in people with Cockayne syndrome. If you have this condition, stop taking metronidazole and contact your doctor if you have signs of liver failure--nausea, stomach pain (upper right side), dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).

Side effects may be more likely in older adults.

Common side effects may include:

depression, trouble sleeping, feeling irritable;
headache, dizziness, weakness;
nausea, vomiting, loss of appetite, stomach pain;
diarrhea, constipation;
unpleasant metallic taste;
rash, itching;
vaginal itching or discharge, pain during sex;
mouth sores; or
swollen, red, or "hairy" tongue.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Dosage Guidelines & Tips

How to take Metronidazole (Flagyl)?

Use Metronidazole (Flagyl) exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Metronidazole oral is taken by mouth.

Metronidazole injection is given as an infusion into a vein. A healthcare provider will give you this injection if you are unable to take the medicine by mouth.

Shake the oral suspension (liquid). Measure a dose with the supplied measuring device (not a kitchen spoon).

Swallow the extended-release tablet whole and do not crush, chew, or break it.

If you are treating a vaginal infection, your sexual partner may also need to take metronidazole so you don't become reinfected.

Metronidazole is usually given for up to 10 days in a row. You may need to repeat this dosage several weeks later.

Keep using this medicine even if your symptoms quickly improve. Skipping doses could make your infection resistant to medication. Metronidazole will not treat a viral infection (flu or a common cold).

Metronidazole will not treat a vaginal yeast infection. You may even develop a new vaginal yeast infection, which may need to be treated with antifungal medication. Tell your doctor if you have symptoms such as itching or discharge during or after treatment with metronidazole.

Do not share this medicine with another person, even if they have the same symptoms you have.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using metronidazole.

Store at room temperature away from moisture and heat.

What should I do if I missed a dose of Metronidazole (Flagyl)?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.