Medically Reviewed by Cheryl Mearig, PharmD.
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Metronidazole, also known by its brand name Flagyl, is an FDA-approved antibiotic and antiprotozoal drug. It’s used to treat various bacterial infections, especially those that affect the:
Metronidazole prescriptions typically come with a warning to avoid drinking alcohol while taking it. Metronidazole can interact with alcohol, causing unpleasant effects.
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Alcohol does not impact the therapeutic effectiveness of metronidazole. But metronidazole can affect how the body handles alcohol.
When the body metabolizes alcohol, it breaks it down into a toxic compound known as acetaldehyde. Your body then uses an enzyme to turn it into acetate.
However, metronidazole stops this enzyme from working, which stops the body from properly metabolizing the alcohol. This toxic build-up of acetaldehyde in the bloodstream causes unpleasant side effects like:
Mixing metronidazole and alcohol also causes a disulfiram-like reaction. Disulfiram treats chronic alcoholism and causes unpleasant side effects whenever you drink alcohol.
This disulfiram-like reaction can cause serious issues. Thankfully, the severe risks are rare and typically only happen if you take the medication for a long time.
These side effects include:
The disulfiram-like reaction can also cause serious skin reactions, such as DRESS syndrome. Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare and severe medication allergy.
Metronidazole is typically prescribed for approximately 10 days. If you drink alcohol during treatment, you’ll be putting yourself at risk for potential side effects.
For most people, metronidazole may still be present in the body up to 40 hours after your last dose. However, it can stay in your body for up to 6 days if you have liver problems.
Because of this, you should avoid alcohol during treatment and 3 days after the last dose. For topical metronidazole, you should avoid alcohol for 24 hours after the last application.
Yes, it is possible to take too much metronidazole and overdose. Symptoms of overdose include:
If you or someone you know thinks they may have taken too much metronidazole, call your doctor or the American Association of Poison Control Centers (1-800-222-1222).
If symptoms are severe, call 911 or head to your nearest emergency room for immediate care.
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The interaction between metronidazole and alcohol isn’t well studied. However, certain people are at risk for the side effects of one substance or the other.
The people at risk for this interaction include:
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In addition to alcohol, metronidazole may interact with other prescription and over-the-counter medications and nutrition supplements.
Tell your doctor about your health and medication history before taking metronidazole. Medications that may interact with metronidazole include:
Metronidazole boosts the efficiency of blood-thinning medications, increasing the risk for abnormal bleeding. Doctors often reduce the dose of a usual blood-thinning medication, such as warfarin, when combined with metronidazole.
Metronidazole can increase sensitivity to the sun. Limiting sun exposure by using sunscreen, wearing hats, and protective clothing is important.
Metronidazole is an antibiotic and antiprotozoal medication used to treat bacterial infections. Drinking alcohol while taking metronidazole results in unpleasant side effects that may range from mild to severe.
Mixing metronidazole and alcohol can create disulfiram-like effects. This reaction can potentially cause serious side effects.
If you want to drink alcohol, wait at least 3 days after your last dose, and 6 days if you have liver problems. If you experience severe side effects or overdose symptoms, seek medical attention.
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