Metronidazole

Medically reviewed by Brittany A. Duke, PharmD, RPh, on April 24, 2023
Written by Sarah Lewis, PharmD

These approved uses differ based on the form of metronidazole prescribed.

This article describes metronidazole’s uses and dosage, ways to save on cost, and more. Below you’ll find some coupon options for metronidazole.

This article doesn’t provide coupons for all forms of metronidazole. To find out more about metronidazole gel, see this article. And to find out more about metronidazole vaginal gel, see this article.

Boxed warnings

The oral and injection forms of metronidazole have a boxed warning about the risk of cancer and the importance of taking the drug only for specific purposes. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

For details, see the “Warnings for metronidazole” section below.

Metronidazole may cause mild or serious side effects. More common mild side effects of metronidazole and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age and overall health and any other medications you take.

To learn more about metronidazole’s side effects, see this article or ask your doctor or pharmacist. You can also read the prescribing information* for metronidazole.

* To view metronidazole’s prescribing information, see the “Article resources” section below.

Mild side effects

More common mild side effects reported with some forms of metronidazole are listed below. These side effects may differ based on the form of metronidazole you take or use. To learn more about metronidazole’s side effects based on form, see the prescribing information* for metronidazole.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Metronidazole oral tablet’s mild side effects include:

• diarrhea
• headache
• loss of appetite
• nausea or vomiting
• mild allergic reaction†

Metronidazole topical cream’s mild side effects include:

• burning or stinging
• itchiness
• skin irritation
• skin redness or discoloration
• mild allergic reaction†

* To view metronidazole’s prescribing information, see the “Article resources” section below.

† For details about this side effect, see the “Warnings for metronidazole” section below.

This article doesn’t include all possible mild side effects of the drug.

Serious side effects

Serious side effects of metronidazole are listed below. These side effects may differ based on the form of metronidazole you take or use. To learn more about metronidazole’s side effects based on form, see the prescribing information* for metronidazole.

With many drugs, serious side effects are possible but not common. If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

In general, metronidazole’s serious side effects include:

• changes in the heart’s electrical system
• joint pain
• nervous system problems, including dizziness, seizures, and loss of coordination
• peripheral neuropathy (burning, numbness, or pain in one or more limbs)
• blood cell problems, which are reversible
• serious skin reactions
• boxed warnings: risk of cancer and the importance of the drug’s use for specific purposes†
• severe allergic reaction†

* To view metronidazole’s prescribing information, see the “Article resources” section below.

† For details about this side effect, see the “Warnings for metronidazole” section below.

These side effects may differ based on the form of metronidazole you take or use. This article doesn’t include all possible serious side effects of the drug.

Below you’ll find answers to a few commonly asked questions about metronidazole.

Can metronidazole be used for dogs?

Yes, veterinarians can prescribe metronidazole for dogs and other animals. This is an off-label use of metronidazole. With off-label use, a medication is prescribed for a use that’s not approved by the Food and Drug Administration (FDA).

You should not give metronidazole to your dog without your veterinarian’s approval. To learn more about using metronidazole in animals, talk with your pet’s vet.

Is it safe to use metronidazole with other antibiotics, such as ofloxacin, ciprofloxacin, or amoxicillin?

Yes, metronidazole can be combined with other antibiotics to treat certain infections. There aren’t any known interactions between metronidazole and ofloxacin, ciprofloxacin (Cipro), or amoxicillin.

Be sure to check with your doctor before taking any new medications. If you’re concerned about drug interactions, you can talk with your doctor or pharmacist. It also helps to fill all your prescriptions at the same pharmacy. This gives your pharmacist a chance to review all the medications you take and check for possible problems.

Can metronidazole be used for diarrhea, a UTI, or an STD?

Yes, metronidazole is approved to treat certain infections that cause diarrhea. It’s also approved to treat a common sexually transmitted disease (STD) called trichomoniasis. But doctors generally don’t use metronidazole to treat urinary tract infections (UTIs).

If you have or think you have any of these infections, see your doctor. They can determine the most likely cause and recommend treatment.

Does metronidazole cause yeast infection or changes in your urine?

Yes, metronidazole can cause a yeast infection of the vagina. Symptoms can include vaginal itchiness, irritation, and white, curd-like discharge.

Metronidazole can also cause urinary symptoms, including:

• painful urination
• urinating more than usual
• dark-colored urine

If you have any of these symptoms, see your doctor. They can recommend treatment to relieve your symptoms.

How does metronidazole work? And how long does it take to start working?

For infections, metronidazole works by killing bacteria and parasites that are causing an infection. This helps clear the infection.

For rosacea, it isn’t exactly clear how metronidazole works. It’s thought to help decrease inflammation (swelling and damage) in the skin.

Metronidazole will start working within a few hours. But it can take a day or two for symptoms to start getting better. It’s important to finish all the doses of metronidazole that your doctor prescribes, even if you feel completely better. If you have an infection, this will help make sure the infection doesn’t come back and become harder to treat.

The Food and Drug Administration (FDA) approves prescription drugs such as metronidazole for certain conditions. Approved uses for metronidazole are described below. These uses differ based on the form of metronidazole prescribed.

Use for rosacea

Doctors may prescribe metronidazole topical cream, gel, or lotion for treating rosacea. It’s used for this purpose in adults. It’s usually prescribed as a long-term treatment.

Rosacea is a long-term inflammatory skin condition. It causes redness or deepening of skin color, as well as small pimple-like bumps on the skin. It usually affects the face, but can also appear on the neck or chest. Without treatment, it can cause the skin to thicken.

Use for certain infections

Doctors may prescribe metronidazole oral tablet, oral capsule, injection, or vaginal gel for treating infections caused by certain bacteria or parasites. It’s used for this purpose in adults and sometimes in children. It’s usually prescribed as a short-term treatment.

With infections, symptoms can vary depending on where the infection is and whether it’s caused by bacteria or a parasite. Metronidazole can help relieve these symptoms by killing the bacteria or parasites that are causing the infection.

Below, you’ll find information about metronidazole’s possible interactions and warnings.

Interactions of metronidazole

For some medications, certain things may affect how the drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take or use metronidazole, ask your doctor to check for possible interactions. They can check for interactions these items may cause with metronidazole. Be sure to tell them about any of the following you take or use:

• prescription medications
• over-the-counter medications
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for metronidazole” section below.

Warnings for metronidazole

Metronidazole should not be taken or should be taken cautiously by certain people.

Boxed warnings

The oral and injection forms of metronidazole have a boxed warning about the risk of cancer and the importance of taking the drug only for specific purposes. Boxed warnings are serious warnings from the Food and Drug Administration (FDA).

To learn more about these warnings, read below. You can also talk with your doctor or pharmacist.

Risk of cancer. In studies,* some animals that took metronidazole got cancer. It isn’t known if this risk applies to humans, but it could. For more information, talk with your doctor or pharmacist.

Use of metronidazole for specific purposes. Metronidazole should only be used for infections that are likely to respond to it. This will help keep the drug effective and prevent drug-resistant bacteria from developing. Drug-resistant bacteria are bacteria that can no longer be killed by a particular drug. For questions about this, talk with your doctor or pharmacist.

* For details about metronidazole’s studies, refer to the prescribing information for the form of metronidazole you’re taking or using. To see the drug’s prescribing information, see “Article resources” below.

Other warnings

Metronidazole could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether metronidazole is a safe option for you. These warnings may differ based on the form of metronidazole you take or use.

Ask your doctor about specific warnings for metronidazole, and be sure to tell your doctor about your:

• current health, including any allergies to medications
• past health conditions and surgeries

Allergic reaction

Metronidazole can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to metronidazole or any of its ingredients, your doctor will likely not prescribe metronidazole. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to metronidazole, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Pregnancy or breastfeeding and metronidazole

Information about metronidazole and pregnancy and breastfeeding is described below.

Metronidazole and pregnancy

Metronidazole oral tablet and oral capsule should not be taken during the first trimester of pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication. Your doctor may suggest birth control options to use during treatment with metronidazole oral tablet or oral capsule.

It’s not known whether other forms of metronidazole should be used during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before using this medication.

Metronidazole and breastfeeding

Metronidazole should not be taken or used while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking or using this medication. Your doctor may recommend other ways to feed your child during treatment with metronidazole.

The dosage of metronidazole your doctor prescribes may vary based on your condition and certain other factors. Talk with your doctor about the dosage you should take or use.

Taking, injecting, and applying metronidazole

Metronidazole oral tablet and oral capsule are taken by mouth.

If you take the extended-release tablet, it needs to be taken on an empty stomach. This means taking it 1 hour before or 2 hours after a meal. Otherwise, metronidazole oral tablet and oral capsule can be taken with or without food. Always follow your doctor’s recommendations.

Metronidazole vaginal gel is given with an applicator into the vagina.

Metronidazole liquid solution is given by a healthcare professional as an intravenous (IV) infusion. This is an injection into a vein that’s given over time. The infusion typically lasts 30 to 60 minutes.

Metronidazole topical gel, lotion, and cream are applied to the skin.

Your doctor will talk with you about how to take or use metronidazole. They’ll explain how much to take or apply and how often. If you’re receiving metronidazole by IV infusion, they’ll explain how metronidazole will be given to you and where you’ll receive it.

Overdose of metronidazole

You should not take or use more metronidazole than your doctor prescribes. For some drugs, doing so may lead to serious side effects or overdose.

If you think you’ve taken or used too much metronidazole, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

You may be able to save money on your prescription for metronidazole by using our Perks discount coupons. These can be found at the end of this article.

If you have questions about how to pay for metronidazole, talk with your doctor or pharmacist. You can also learn more about the cost of metronidazole in this article.

Note: Optum Perks coupons cannot be used with insurance copays or benefits.

This article describes metronidazole’s uses and dosage, ways to save on cost, and more. Let your doctor know if you have questions about metronidazole or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• Do any of the other medications I take interact with metronidazole?
• How long will I need to take or use metronidazole?
• What can I do to manage common side effects of metronidazole?

• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Metronidazole – metronidazole capsule. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/387053e5-7eda-4282-b58a-5789430a2e99/spl-doc
• Metronidazole- metronidazole cream. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/43ed872b-63ac-4a22-9c9e-cc0e05bcc41e/spl-doc
• Metronidazole- metronidazole gel topical. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/a0d7d4e8-28c0-4211-8d76-73a173b48d9a/spl-doc
• Metronidazole- metronidazole gel vaginal. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/71a4f384-4211-4a69-90e6-c6a0cdd4d97d/spl-doc
• Metronidazole- metronidazole injection, solution. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/df7df946-c83f-4adf-9007-aff4f757a665/spl-doc
• Metronidazole- metronidazole lotion. (2022). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/5368755a-dd37-4e34-843f-ece6bac8ef6a/spl-doc
• Metronidazole- metronidazole tablet. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/aea4e2a1-2089-40dc-9eee-deaab4f21397/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.