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Metronidazole is currently the 28th most commonly prescribed drug in the United States, according to ClinCalc. In 2017 alone, doctors wrote 12,657,176 prescriptions for metronidazole. Considering how popular this drug is right now, it pays to know a little bit more about this medication, including how long metronidazole stays in your system.

The FDA states the following information regarding metronidazole half-life:

  • Mean effective half-life: 8 hours

Metronidazole has an oral bioavailability of more than 90 percent, which means the body absorbs about 90 percent of the available metronidazole in a pill or tablet. The liver breaks down metronidazole into five components, or metabolites. The body then eliminates most of metronidazole and these metabolites in urine and feces.


What is the half-life of metronidazole?

The elimination half-life of metronidazole is eight hours in a healthy individual, according to the Food & Drug Administration (FDA). This fact means it takes eight hours for the liver to break down and eliminate half of the metronidazole from the body.

How long does metronidazole stay in your system?

This drug may be detectable in your system for up to 44 hours.

  • Urine: Up to 80% of this drug (500 mg injection) is excreted both as unchanged metronidazole and its metabolites via urine, with a kidney clearance of 10 mL/min/1.73 m2.
  • Plasma: Peak concentrations occur roughly 1 to 2 hours after the last dose (Flagyl® tablets)

How long does it take for metronidazole to get out of your system?

It takes approximately 5.5 times the elimination half-life for a medicine to clear completely from the body. The elimination half-life of metronidazole is eight hours, so it will take about 44 hours (5.5 x 8 = 44) to clear this drug from the system.

Can I drink alcohol 24 hours after taking metronidazole?

No; drinking alcohol 24 hours after taking metronidazole can cause an uncomfortable and sometimes serious reaction, known as a disulfiram-like reaction, according to the National Library of Medicine. This reaction can cause flushing, rapid heartbeat, irregular heartbeat (palpitations), nausea, and vomiting. Some experts advise waiting at least 48 hours after the last dose to have any alcohol.

Can I drink alcohol 12 hours after taking metronidazole?

No; doing so may cause a disulfiram-like reaction (see above). Most experts advise that people wait at least 48 hours/2 days after their last dose before drinking.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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