Just about every medication we take comes with side effects. Sometimes, those effects are minor annoyances, such as headaches, diarrhea, or tiredness.
Other times, severe symptoms (allergic reactions or severe vomiting) might call for a discussion with the doctor about stopping the medication or switching to a different one.
The antibiotic metronidazole (Flagyl) is one medication that can cause certain side effects.
It works against serious conditions such as bacterial vaginosis, sexually transmitted infections (STIs) like trichomoniasis, and sometimes Clostridiodes difficile (a gastrointestinal) infection.
But metronidazole can have its own side effects, including diarrhea, nausea, and headache.
Most bacterial and parasitic infections won’t go away on their own. It’s critical to follow your doctor’s prescription instructions.
If you don’t complete your treatment, the infection could get worse, and you’ll have a greater chance of developing antibiotic resistance.
Does metronidazole cause diarrhea and nausea?
Diarrhea and nausea were two of the most commonly reported side effects of metronidazole in the drug’s studies. Nausea was more common than diarrhea.
As an antibiotic, metronidazole gets rid of the bacteria in your body that’s causing an infection. However, it may also target the healthy bacteria that live in your gut.
This can lead to gastrointestinal side effects, such as diarrhea and nausea, alongside stomach pain. But these side effects are usually mild and relatively manageable.
In rare cases, antibiotics like metronidazole can cause a condition called Clostridiodes difficile-associated diarrhea (CDAD). This happens when the medication disrupts the usual balance of bacteria in your gut, leading to an overgrowth of harmful bacteria that release toxins.
CDAD can cause severe, long-lasting diarrhea and, in some cases, serious complications. If you develop frequent watery diarrhea that doesn’t improve after stopping metronidazole, or if you notice blood in your stool, contact your doctor right away.
You can take metronidazole with or without food, but taking it with food may help minimize uncomfortable stomach symptoms and settle your stomach.
Stay hydrated and stick with a bland diet while you’re on this antibiotic to avoid irritating your stomach more.
You might consider avoiding all alcohol while taking metronidazole or other antibiotics.
It can increase your risk of side effects from metronidazole, including diarrhea and vomiting. And it can potentially be dangerous. Your doctor will likely advise you to avoid alcohol during treatment with metronidazole and for 3 days after finishing treatment.
“You need to be extra careful with other alcohol-containing products, like cough and cold remedies,” said Stefanie Ferreri, PharmD, and chair of the practice advancement and clinical education division at UNC Eshelman School of Pharmacy in Chapel Hill, North Carolina.
“You can have severe nausea and vomiting if you mix the two and may have a nasty hangover afterward as well.”
Finally, you might also consider taking an over-the-counter probiotic. Probiotics can be beneficial in keeping your gut healthy, and taking probiotics may help prevent the diarrhea that often accompanies antibiotic treatment.
Other side effects
Alongside gastrointestinal side effects like diarrhea and nausea, metronidazole can cause other side effects. Some of the most common include:
- headaches
- dizziness
- confusion
- nerve pain known as peripheral neuropathy
One common, slightly bizarre side effect is a metallic taste in your mouth. Doctors don’t know why this happens, but it isn’t harmful, and it should go away on its own after you finish treatment.
But it can be unpleasant, so you might want to suck on lemon drops or mints, use mouthwash, and brush your teeth regularly while taking metronidazole. Taking the drug with food you enjoy can also prevent this side effect.
Metronidazole can lead to more serious side effects as well, including having a black box warning for its risk of leading to cancer. However, such serious side effects are very rare.
Metronidazole is generally safe and well tolerated. Research suggests that lower doses are effective while causing fewer and milder side effects than higher doses.
How to get metronidazole out of your system faster
A typical course of metronidazole depends on what it’s treating, but it typically won’t be longer than 14 days, and it’s more likely to be around 7 to 10 days.
It’s important to finish your course of antibiotics even if you feel better to prevent the infection from returning.
The half-life of metronidazole (that is, the amount of time it takes for half of the drug to leave your body) is 8 hours.
According to the National Institutes of Health (NIH), it takes around 4 to 5 half-lives for a drug to completely leave your body.
Once you’ve finished your treatment, you can try to get the drug out of your system faster by making sure you drink plenty of water. But it may be best to let the drug work and leave your system naturally.
How long does it take for metronidazole side effects to go away?
Metronidazole is usually taken for up to 10 days, though some conditions may require longer treatment. The medication has an 8-hour half-life, so it will typically leave the body within 1 to 2 days after the last dose. However, if you have a liver or kidney problem, or if you are an older adult (ages 65 years and older), it may take longer for your body to clear the drug.
Most side effects, like nausea or headache, should go away after you stop taking metronidazole. However, some side effects can last longer. This is especially true for nerve-related effects, such as numbness or tingling.
If you have side effects that persist for several days after finishing treatment, talk with your doctor. They can help determine whether your symptoms are related to metronidazole or another cause and suggest ways to manage them.
Alternatives
A doctor will prescribe you an antibiotic based on what it’s treating. But several may be appropriate depending on the condition and your individual situation. Other common antibiotics include:
- amoxicillin (Amoxil)
- doxycycline (Adoxa)
- ceftriaxone (Rocephin)
- levofloxacin (Levaquin)
Note that side effects, particularly milder ones like diarrhea and nausea, are common to most antibiotics. But they can affect everyone differently.
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Like any medication, metronidazole can cause side effects ranging from mild to more serious. Some of the most common side effects include diarrhea and nausea. It can also cause a metallic taste in your mouth.
These side effects usually go away on their own after you finish your treatment. Making sure you take the drug with food and avoiding alcohol for the duration of treatment can help prevent or ease these effects.
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Download the free Optum Perks Discount Card to save up to 80% on many prescription medications. Plus, you can now get them delivered to your home in as little as 3 days. Search for your medication here.