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Metronidazole is an effective antibiotic that treats infections caused by bacteria and parasites. This medicine must not be used to treat flu, colds, or infections caused by viruses. Several bacterial infections occurring in your respiratory tract, stomach, vagina, skin, and intestines can be treated with this medicine.

Metronidazole also treats infected leg ulcers, pressure sores, and stomach ulcers, which Helicobacter Pylori causes. Doctors prescribe this medicine for treating urinary or genital infections, which are caused by Trichomonas parasites and amoebiasis. To prevent infections after surgery effectively, doctors give this medicine to patients.

This medicine is available under different brand names, including Flagyl, Flagyl ER, and Flagyl IV RTU. It comes in different forms, such as an oral tablet, oral capsule, injectable medication, and extended-release tablets. 

Metronidazole tablets and capsules are also given to treat sexually transmitted diseases. Extended-release tablets are used to treat bacterial vaginosis in women. It belongs to a class of drugs known as Nitroimidazole that helps stop bacteria growth. 

Using antibiotics when they are not required often increases the risk of getting an infection that later resists antibiotic treatment. 

What are the uses of Metronidazole? 

Flagyl is used for treating a variety of infections including:

  • Bacterial infections in the lungs, liver, stomach, heart and bloodstream
  • Skin infections like wounds, skin ulcers, rosacea, sores and skin ulcers
  • Bacterial vaginosis and trichomonas vaginal infections
  • Mouth infections such as dental abscesses, inflamed & infected gums, inflamed and others
  • Pelvic inflammatory diseases like PID occur when infection-carrying bacteria travel from the vagina or cervix to the reproductive organs of a woman.

How does Metronidazole work in your body? 

Metronidazole is a Nitroimidazole antibiotic that affects the DNA of bacteria or parasites that cause infection. This further leads to the death of bacteria and stops their growth in your body. 

How to take Metronidazole? 

Follow the directions mentioned on the prescription label carefully, and if there is any doubt, then discuss it with the doctor. Metronidazole comes as a tablet, an extended-release tablet, and as a capsule that is taken by mouth.  

These tablets are taken as a one-time dose or two to four times regularly for ten days or longer. Extended-release tablets are generally taken once daily, almost 1 hour before or 2 hours after a meal for one week. 

Based on the infection being treated, your age, and your body's response to treatment, the doctor will determine the correct dosage of this medicine. Patients suffering from severe hepatic impairment must reduce their dosage to 50%. 

This medicine will not treat your vaginal yeast infection. You might develop a new vaginal yeast infection that needs to be treated with an antifungal drug. In case you experience symptoms like discharge or itching during or after treatment with this medication.

When treating a vaginal anaerobic bacterial infection, your sexual partner also requires to take this antibiotic so that you are not reinfected. Do not share this antibiotic with another person, even if they have the same symptoms you have. 

Metronidazole is mainly given for ten days in a row. You might be required to repeat this dosage for several weeks later. 

Missed dose

If you have missed a dose, then take it as soon as you remember. But skip missed dosage if it's already time for your next scheduled dose. 

Do not take two doses at the same time just to make up a missed one, as this will lead to an overdose. 


Get emergency medical help if you suffer from an overdose of Metronidazole. 

Overdose symptoms include vomiting, numbness, nausea, tingling, or problems with muscle movement. 

Precautions and warnings

Do not take Metronidazole if you are allergic to it or have any other kind of allergy, like rashes, hives, or others. 

Before starting treatment with this medicine, inform the doctor about your medical history, especially of:

  • Certain blood disorders like low blood cell counts
  • Liver disease
  • Kidney disorder
  • A specific rare genetic disorder like Cockayne syndrome

Avoid alcoholic beverages and products that contain propylene glycol when taking Metronidazole and for almost three days after finishing treatment; this is because you can suffer from headaches, severe stomach cramps, nausea, flushing, and vomiting. This Drug can also make live bacterial vaccines not work effectively. Inform the doctor before having any vaccinations about using this medication. 

It is suggested to avoid the consumption of alcohol and tobacco products during your treatment with these tablets. 

Consuming alcohol can also cause some severe reactions like dizziness. Take these tablets after having meals to avoid nausea and vomiting. Also, drink enough water to avoid dehydration. 

What are the Side effects of Metronidazole?

Like other antibiotics, Metronidazole can also cause some minor and significant side effects. However, minor side effects start to disappear after your body adjusts to this medication. 

Some common side effects of Metronidazole include:

  • Constipation
  • Dry mouth
  • Headache 
  • Loss of appetite
  • Mouth or tongue irritation
  • Vomiting
  • Diarrhea
  • Stomach problems
  • Nausea

Call the doctor immediately if any of your side effects persist or become worse with time. 


Drug interaction can alter the working mechanism of Metronidazole or even decrease its effectiveness. You must inform the doctor beforehand about all other products you use, including prescription & non-prescription medicines and herbal supplements. 

Several other medicines interact with Metronidazole, including:

  • Lapatinib
  • Felbamate 
  • Doxepin
  • Itraconazole 
  • Alfuzosin
  • Buprenorphine 
  • Crizotinib


Metronidazole should be stored at room temperature, away from direct heat, light, and moisture. 

Always store this medicine in a dry place. 

Frequently asked questions about Metronidazole (FAQs)

Is it safe to drink alcohol while using Metronidazole? 

No, avoid alcohol consumption when taking Metronidazole. You must also avoid alcohol after three days of completing treatment. 

Intake of alcohol can make you suffer from an unpleasant reaction with symptoms like vomiting, flushing, stomach pain, and headache. 

How long does Metronidazole take to work in your body? 

Generally, Metronidazole begins to work within 1 hour of its consumption. This medicine might take 2-3 days to make you feel better. 

In case you do not experience any noteworthy reduction in your symptoms, then contact a doctor immediately. 

What if there is no improvement in your condition after using Metronidazole? 

Let your doctor know if you do not feel better after completing a course of treatment with Metronidazole. 

Also, if your symptoms start to become worse during treatment, then stop this medicine and talk to a doctor. 

Does the use of Metronidazole cause a metallic taste? 

Yes, Metronidazole might cause a temporary metallic taste. However, this taste can be reduced by staying hydrated and brushing your teeth after meals. 

Can I stop my treatment with Metronidazole when I feel better? 

No, do not stop taking this medicine and complete an entire course of treatment even if you start feeling better after a few days. 

Your symptoms might improve before the infection is cured completely. But stopping treatment in between can cause your infection to return. 

Before you stop taking Metronidazole, consult a doctor and follow their advice.