This article describes possible interactions with metronidazole oral tablet. Interactions can cause a drug to have a different effect on the body than expected. Interactions can occur due to medications, alcohol, or certain health conditions.
Metronidazole comes in the following forms:
- tablets and capsules that you’ll swallow
- a solution for injection into a vein
- topical forms that are applied to the skin
- a gel that’s applied to the vagina
Interactions of metronidazole may vary depending on the form of metronidazole you’re prescribed.
Boxed warning
This drug has a boxed warning about the risk of cancer and the importance of only taking the drug for specific purposes. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
See the end of this article for more information about this warning.
Other drugs and metronidazole
The drugs in the list below may interact with metronidazole oral tablet. This article doesn’t include all drugs that may interact with metronidazole.
Drug classes or drugs that may interact with metronidazole oral tablet include:
- certain antiarrhythmic drugs (medications used to treat irregular heart rhythm):
- drug examples: amiodarone (Pacerone), quinidine
- what might happen: can increase the risk of side effects with metronidazole and the antiarrhythmic drug
- certain antibiotics:
- drug examples: erythromycin (Eryc, Ery-Tab, and others), moxifloxacin
- what might happen: can increase the risk of side effects of metronidazole and the antibiotic drug
- certain antidepressants:
- drug examples: citalopram (Celexa), trazodone
- what might happen: can increase the risk of side effects of metronidazole and the antidepressant drug
- certain antipsychotic drugs:
- drug examples: ziprasidone (Geodon), quetiapine (Seroquel)
- what might happen: can increase the risk of side effects of metronidazole and the antidepressant drug
- seizure medications:
- drug examples: phenytoin and phenobarbital
- what might happen: can decrease the effect of metronidazole
- busulfan (Myleran), a chemotherapy drug:
- what might happen: can increase the risk of side effects of busulfan
- disulfiram, a medication for treating alcohol dependence:
- what might happen: can increase the risk of side effects of metronidazole
- lithium (Lithobid):
- what might happen: can increase the effect and risk of side effects of lithium
- methadone (Methadose):
- what might happen: can increase the risk of side effects of metronidazole and methadone
- warfarin (Jantoven):
- what might happen: can increase the effect and risk of side effects of warfarin
- cimetidine:
- what might happen: can increase the effect and risk of side effects of metronidazole
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When to avoid metronidazole
Certain health conditions or other factors could increase some risks with metronidazole oral tablet. Doctors may not prescribe metronidazole in these cases. These health conditions or other factors are called contraindications.
Here’s a list of contraindications for metronidazole oral tablet:
- Cockayne syndrome: If you have Cockayne syndrome, taking metronidazole oral tablet may cause severe or even life threatening side effects, including permanent liver failure.
- Current or recent use of the drug disulfiram: If you take disulfiram or have taken it within the past 2 weeks, taking a metronidazole oral tablet may cause symptoms of psychosis as a side effect.
- Drinking alcohol and taking metronidazole: Drinking alcohol while taking metronidazole can cause side effects, including severe nausea, vomiting, headaches, and abdominal cramps. If you drink alcohol, avoid it for at least 3 days after your last dose of metronidazole.
- Past allergic reaction to metronidazole: If you’ve ever had an allergic reaction to metronidazole oral tablet, taking it again may cause another allergic reaction.
Before you start taking metronidazole, tell your doctor if any of these contraindications relate to you. They can recommend whether you should take metronidazole.
Alcohol and metronidazole
Metronidazole oral tablet is known to interact with alcohol. If you drink alcohol, you should not consume it while taking metronidazole.
Metronidazole interactions with alcohol may cause severe:
- nausea and vomiting
- headaches
- abdominal cramps
You should avoid drinking alcohol for at least 3 days after your last dose of metronidazole. If you have concerns about avoiding alcohol while taking metronidazole oral tablet, talk with your doctor.
Other interactions and metronidazole
Interactions can occur with supplements, foods, vaccines, and some lab tests. Keep reading to learn whether metronidazole oral tablet has these interactions.
The following information doesn’t include all possible interactions with metronidazole.
Metronidazole and supplements
Before taking metronidazole oral tablet, tell your doctor and pharmacist about any herbs, vitamins, and supplements you take. Doing so may help you avoid interactions.
If you have questions about interactions that may affect you, talk with your doctor or pharmacist.
Metronidazole interactions with herbs
Metronidazole oral tablet may interact with herbal supplements that can affect your heart rhythm. Taking metronidazole and using these supplements may lead to long QT syndrome, a serious irregular heart rhythm.
Examples of herbs that can cause this interaction with metronidazole include:
Talk with your doctor or pharmacist before taking any herbal supplement while taking metronidazole oral tablet.
Metronidazole interactions with vitamins
Metronidazole oral tablet isn’t known to interact with any vitamins. But this doesn’t mean interactions with vitamins can’t happen or won’t be identified later.
Talk with your doctor or pharmacist before taking any of these products while taking metronidazole oral tablet.
Metronidazole interactions with food
Metronidazole oral tablet isn’t known to interact with foods. But this doesn’t mean interactions with foods can’t happen or won’t be identified later.
Talk with your doctor or pharmacist if you have additional questions about what foods to avoid while taking metronidazole.
Metronidazole and vaccines
Metronidazole oral tablet isn’t known to interact with any vaccines. But this doesn’t mean interactions with vaccines can’t happen or won’t be identified later.
Talk with your doctor or pharmacist before receiving any vaccines while taking metronidazole oral tablet.
Metronidazole and lab tests
Metronidazole oral tablet may interact with numerous blood tests and cause them to have an inaccurate result. Examples include blood tests used to check:
Talk with your doctor or pharmacist before having any tests while taking metronidazole oral tablet.
Metronidazole and cannabis or CBD
Metronidazole oral tablet isn’t known to interact with cannabis (commonly called marijuana) or cannabis products such as cannabidiol (CBD). But this doesn’t mean interactions can’t happen or won’t be identified later.
As with any drug or supplement, tell your doctor before taking cannabis with metronidazole.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Health factors and metronidazole
Certain medical conditions or other health factors may increase the risk of interactions with metronidazole oral tablet. Keep in mind that interactions could lead to side effects or affect how well the drug works. Before taking metronidazole, tell your doctor about your health history. They’ll determine whether metronidazole is right for you.
Interactions with metronidazole oral tablet may occur with the following:
- blood cell conditions, such as low white blood cell level
- Cockayne syndrome
- epilepsy or seizures
- kidney conditions, such as chronic kidney disease
- liver conditions, such as alcohol-related liver disease
- long QT syndrome
- pregnancy or breastfeeding
- past allergic reaction to metronidazole
Questions about metronidazole and interactions
Here you’ll find answers to some common questions about metronidazole and possible interactions.
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Get free cardAre there interactions between metronidazole and birth control?
Possibly. It’s not known for certain whether there are interactions between metronidazole oral tablet and birth control.
Some studies show that antibiotics may cause birth control pills containing both estrogen and progesterone to be less effective. (Keep in mind that metronidazole is an antibiotic.) However, other studies haven’t shown this. Because of the possible risk of unintended pregnancy, your doctor or pharmacist may recommend using an alternative or backup contraceptive while you’re taking metronidazole.
Talk with your doctor or pharmacist if you have additional questions about birth control and possible interactions with metronidazole.
What pain medications can I take with metronidazole?
Most pain relievers don’t interact with metronidazole oral tablet. So they should be safe to take if your doctor agrees that a pain medication is safe for you.
But metronidazole does interact with methadone. Methadone is an opioid drug that your doctor may prescribe to treat severe pain. They may also prescribe it to treat opioid use disorder. Taking metronidazole and methadone can increase the risk of serious side effects. Due to this risk, doctors try to avoid prescribing metronidazole and methadone together.
Talk with your doctor or pharmacist to learn more about whether a certain pain reliever is safe to take with metronidazole.
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Preventing metronidazole interactions
It may be possible to avoid certain interactions with metronidazole oral tablet. Before taking this drug, you can discuss possible interactions with your doctor and pharmacist.
Things to consider include:
- Whether you drink alcohol or use cannabis.
- Other medications and herbs you take, as well as vitamins and supplements. Your doctor or pharmacist can help you fill out a medication list.
- What to do if you’re prescribed a new drug while taking metronidazole oral tablet.
Taking metronidazole exactly as prescribed can also help prevent interactions.
Boxed warning for metronidazole
This drug has a boxed warning about the risk of cancer and the importance of taking the drug only for specific purposes. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
Risk of cancer and importance of only taking the drug for specific purposes: Animal studies have shown that metronidazole may increase the risk of cancer. It’s not known whether the drug also causes this effect in humans.
Because of this risk, metronidazole should only be used to treat a bacterial or parasitic infection for which the drug is known to work. Doctors do not recommend taking this drug for nonapproved uses.
To learn more about this warning, talk with your doctor.
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.