Class Name(s):

• 8:30.16.92 Nitroimidazole Derivatives, Miscellaneous

Pronunciation:

• (me troe ni' da zole)

Brand Name(s):

• Flagyl^® I. V.¶
• Flagyl^® I. V. RTU^®; also available generically

IMPORTANT WARNING:

Metronidazole injection can cause cancer in laboratory animals. Talk to your doctor about the risks and benefits of using this medication.

WHY is this medicine prescribed?

Metronidazole injection is used to treat certain infections caused by bacteria. Metronidazole injection is also to prevent infection when used before, during, and after colorectal surgery. Metronidazole injection is in a class of medications called nitroimidazole antibacterials. It works by killing bacteria and protozoa that cause infection.

Antibiotics such as metronidazole injection will not work for colds, flu, or other viral infections. Taking antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.

HOW should this medicine be used?

Metronidazole injection comes as a solution and is infused (injected slowly) intravenously (into a vein) over 30 minutes to 1 hour. It is given every 6 hours. The length of treatment depends on the type of infection being treated. Your doctor will tell you how long to use metronidazole injection.

You may receive metronidazole injection in a hospital, or you may use the medication at home. If you will be using metronidazole injection at home, your health care provider will show you how to infuse the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions.

You should begin to feel better during the first few days of treatment with metronidazole injection. If your symptoms do not improve or if they get worse, call your doctor.

Use metronidazole injection until you finish the prescription, even if you feel better. If you stop using metronidazole injection too soon or if you skip doses, your infection may not be completely treated and the bacteria may become resistant to antibiotics.

Are there OTHER USES for this medication?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before using metronidazole injection,

• tell your doctor or pharmacist if you are allergic to this medication, any part of this medication, or any other medications, foods or substances. Tell your doctor or pharmacist about the allergy and what symptoms you had.
• tell your doctor or pharmacist if you are taking the following medication or have stopped taking it within the past two weeks: disulfiram. Your doctor will probably tell you not to use metronidazole injection if you are taking this medication or have taken it within the last 2 weeks.
• you should know that some medications should not be taken with metronidazole injection. Other medications may cause dosing changes or extra monitoring when taken with metronidazole injection. Make sure you have discussed any medications you are currently taking or plan to take before starting metronidazole injection with your doctor and pharmacist. Before starting, stopping, or changing any medications while receiving metronidazole injection, please get the advice of your doctor or pharmacist.
• you should know that the following nonprescription product may interact with metronidazole injection: cimetidine. Be sure to let your doctor and pharmacist know that you are taking these medications before you start receiving metronidazole injection. Do not start any of these medications while receiving metronidazole injection without discussing with your healthcare provider.
• tell your doctor if you have or have ever had Crohn's disease (a condition in which the body attacks the lining of the digestive tract, causing pain, diarrhea, weight loss, and fever), a yeast infection, edema (excess fluid held in body tissues), or blood, kidney, or liver disease.

tell your doctor if you or your child has Cockayne syndrome (a serious genetic disorder). Your doctor will probably tell you that you or your child should not take metronidazole.

• remember not to drink alcoholic beverages or take products with alcohol or propylene glycol while receiving metronidazole injection and for at least 3 days after treatment is finished. Alcohol and propylene glycol may cause nausea, vomiting, stomach cramps, headache, sweating, and flushing (redness of the face) when taken during treatment with metronidazole injection.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while using metronidazole injection, call your doctor.

What SPECIAL DIETARY instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Metronidazole injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea, vomiting, diarrhea
• stomach pain and cramping; constipation
• weakness; headache; irritability; depression
• difficulty falling asleep or staying asleep
• dry mouth; sharp, unpleasant metallic taste; loss of appetite
• furry tongue; mouth or tongue irritation
• redness, pain, or swelling at the injection site

Some side effects can be serious. If you experience any of these symptoms, stop using metronidazole injection and call your doctor immediately:

• rash, itching, hives
• skin blistering, peeling, or shedding in the area; blisters or sores in your mouth; redness or swelling of your face, hands, or soles of your feet; muscle or joint aches
• flushing
• seizures; confusion; fainting; problems with coordination
• numbness, pain, burning, or tingling in your hands or feet
• fever, eye sensitivity to light, stiff neck
• difficulty speaking
• hearing loss; ringing in ears; dizziness

Metronidazole injection may cause other side effects. Call your doctor if you have any unusual problems while using this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I do in case of OVERDOSE?

In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.

Symptoms of overdose may include:

1. nausea, vomiting
2. poor balance; unable to control muscles; confusion; seizures
3. numbness, pain, burning, or tingling in your hands or feet

What should I know about STORAGE and DISPOSAL of this medication?

Your healthcare provider will tell you how to store your medication. Store your medication only as directed. Make sure you understand how to store your medication properly.

Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach http://www.upandaway.org

Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website http://www.fda.gov/drugs/safe-disposal-medicines/disposal-unused-medicines-what-you-should-know for more information.

What OTHER INFORMATION should I know?

Before having any laboratory test, tell your doctor and the laboratory personnel that you are receiving metronidazole injection.

Do not let anyone else take your medication. Your prescription is probably not refillable. If you still have symptoms of infection after you finish the metronidazole injection, call your doctor.

Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.

^¶ This branded product is no longer on the market. Generic alternatives may be available.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™ Copyright, 2026. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: August 15, 2026.