How long do metronidazole’s side effects last?

Metronidazole (Flagyl) is a generic antibiotic drug used to treat certain infections caused by bacteria or parasites, such as:

• certain sexually transmitted infections (STIs)
• certain gastrointestinal infections
• skin and soft tissue infections
• bone and joint infections

Metronidazole comes in multiple forms, including forms that you take by mouth, forms that you apply to your skin, and an injection given by a healthcare professional.

You will need a prescription from your doctor to get metronidazole. It is not available over the counter (OTC).

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Do metronidazole side effects go away?

Like all drugs, metronidazole may cause side effects. Most side effects should go away after you stop taking the drug. But some may last longer.

The most commonly reported side effects of metronidazole include:

• nausea
• headache
• appetite loss
• diarrhea
• metallic taste

Most of these side effects typically last a few days and will likely go away on their own, especially if you only take metronidazole for a short time.

However, if you’re taking metronidazole for a long time, it’s possible to have side effects that last longer. If you have side effects that don’t go away several days after you’ve finished treatment, let your doctor know. They can help determine whether your symptoms are related to metronidazole and suggest ways to help manage them.

Do metronidazole side effects last even after you stop taking the drug?

While it is possible for metronidazole’s side effects to last even after you stop taking the drug, it is rare.

These kinds of side effects are called long-term side effects. They typically start either during the treatment and continue for a long time, possibly even after you’ve stopped the treatment. Or they may start after you’ve taken the drug for a long time and have ended treatment.

Some side effects that may last after you stop taking metronidazole include:

• Encephalopathy: Encephalopathy is a type of damage that occurs to your brain. This side effect typically goes away when you stop taking metronidazole. But it can take up to a few weeks to fully go away.
• Peripheral neuropathy: Peripheral neuropathy involves damage to the nerves outside of your brain or spinal cord. It typically goes away when you stop taking metronidazole. But on some rare occasions, its symptoms may last longer.
• Optic neuritis: Optic neuritis involves damage to your optic nerve. Depending on how severe this damage is, you may need long-term treatment.

Metronidazole has a boxed warning for the risk of cancer. Boxed warnings are serious warnings from the Food and Drug Administration (FDA). In studies, researchers found that metronidazole caused cancer in mice and rats. Because of this, there may be potential for cancer in humans as well. Keep in mind that the effects seen in animals aren’t always the same in humans. Metronidazole has been safely used in humans for an extended period without any notable increase in cancer risk.

Talk with your doctor or pharmacist to learn more about your risk of long-term side effects with metronidazole.

How do I overcome the side effects of metronidazole?

Your doctor can give you personalized advice if you’re experiencing side effects from metronidazole. The best way to overcome or manage metronidazole’s side effects will depend on the side effects you are experiencing.

Some tips that may help you avoid experiencing side effects while taking metronidazole are as follows:

• Take metronidazole with food: This may help you minimize or avoid experiencing uncomfortable stomach side effects.
• Drink lots of water and try to stick to a bland diet: Staying hydrated and eating easily digestible foods may help avoid irritating your stomach more while taking this drug
• Consider avoiding alcohol: Alcohol may increase your risk of side effects like diarrhea and vomiting. Your doctor will likely advise you to avoid alcohol during your treatment with metronidazole and for 3 days after finishing treatment, as it can potentially be dangerous.
• Take a probiotic: An OTC probiotic can help keep your gut healthy. It may also help prevent side effects like diarrhea.
• Add a flavor or eat foods that you enjoy: Having mint, using mouthwash, eating a snack, or drinking something with a flavor you enjoy in combination with metronidazole may help mask the metallic taste that metronidazole may cause.

How long until metronidazole is out of your system?

You will typically take metronidazole for 7 to 14 days, but your exact dosing schedule will depend on what condition you’re taking it to treat. Metronidazole has a half-life of 8 hours, meaning it takes around 8 hours for half of the drug to leave your body. It usually takes 4 to 5 half-lives to get a drug completely out of your system. So, it should take about 2 days for metronidazole to leave your body after you stop taking it.

Once you’ve finished your treatment, you can try to get metronidazole out of your system faster by drinking plenty of water. Make sure you finish your entire course of metronidazole, even if you feel better. This will help prevent the infection from returning.

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Summary

Most of metronidazole’s most common side effects should only last a few days and will likely go away on their own or when you stop taking the drug. This happens especially if you only take metronidazole for a short time. Metronidazole should be fully out of your system around 2 days after you stop taking it.

Side effects that last longer or continue after you stop taking the drug are possible, but they are rare.

Taking metronidazole with food and staying well hydrated during your treatment may help avoid certain side effects.