Metronidazole (Flagyl Flagyl ER) GI

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Metronidazole® (met roh NID ah zole) is the generic name for Flagyl (FLAH jel). This medicine is an antibiotic that is used to treat illnesses like giardiasis (JEE are DIE ah sis) and inflammatory bowel disease. Symptoms should get better after 3 to 5 days of treatment.

How to Give This Medicine

  • If your child takes the liquid form of this medicine, shake well before using it.
  • Use a pediatric measuring device (available at the pharmacy) or a measuring spoon to measure the exact dose. Do not measure liquid medicines in kitchen spoons.
  • Read the label carefully and make sure you are giving your child the right dose. It is easy to confuse the many different dosage forms and strengths.
  • Give the exact dose of medicine that your doctor ordered.
  • Stay with your child until he or she has swallowed the dose of medicine.
  • Ask your pharmacist, nurse or doctor before crushing any medicine.
  • This medicine should be given 1 hour before or 2 hours after If stomach upset occurs, you may give it with food.
  • It is very important to finish all the medicine that is ordered for _____ days. Do not stop the medicine early, even if your child is feeling better.

If You Forget to Give a Dose

If you forget to give a dose of this medicine, give it as soon as possible. Give the rest of the doses at evenly spaced times during the day. Do not double the next dose. Instead, go back to your regular dosing schedule. If you have any questions about this, check with your child's doctor or pharmacist.

If a Dose Is Vomited

  • If your child gags or chokes and spits out the dose before swallowing it, let him calm down and then give the same amount one more time.
  • If the medicine is thrown up (vomited) right after you give it, do not repeat the dose. Some of the medicine may still be in the stomach. The vomiting might be due to the strong taste of the medicine. For the next scheduled dose, try giving the medicine in applesauce or jelly. If the vomiting continues, call your child's doctor.

Medicine Storage

  • Store all medicine out of the reach of children.
  • Always keep medicine in the original bottle from the pharmacy.
  • Keep this medicine in the refrigerator or at room temperature. Do not freeze.
  • Light and moisture make this medicine not work as well. Keep the bottle tightly closed and store it in a dark, dry place (not in the bathroom or above the kitchen sink).
  • Keep this medicine away from heat or direct sunlight.
  • Do not use this medicine after the expiration date printed on the container.
  • When the medicine is no longer needed, mix the leftover medicine with material you are going to throw away, like coffee grounds. Put that mixture into a container or a bag that will not leak. Throw the container away in the trash where children and pets cannot reach it.
  • The liquid form of this medicine is good for 60 days.

Drug – Nutrient Interactions

read the label

  • Your child should not drink alcohol. This medicine, combined with alcohol, can cause severe nausea, cramps, headache and vomiting and flushing (redness of the face) and can be dangerous. Some cold medicines, cough syrups and mouthwashes contain alcohol (Picture 1).
  • Check with your doctor or pharmacist before giving over-the-counter medicines. Do not give products containing alcohol for another 2 days after your child has finished metronidazole.
  • There are many prescription and over-the-counter medicines that should not be taken with metronidazole.  Let your child’s doctor and pharmacist know about all medicines your child takes to make sure they are safe to take with metronidazole.

Special Note for Female Patients

  • If a patient thinks she might be pregnant, she should tell the doctor before she starts taking this or any medicine. This medicine may cause problems if taken during pregnancy.
  • If a patient is breast-feeding her baby, she should tell her doctor before she starts taking this or any medicine. This medicine can be in the breast milk and cause side effects in the baby.

Possible Side Effects

  • Brown-colored urine
  • Rash
  • Numbness or tingling of fingers or toes
  • “Metal” taste in the mouth or dry mouth
  • Nausea or loss of appetite
  • Diarrhea
  • Vomiting (not common)
  • “Metal” taste in the mouth or dry mouth

What to Do About Side Effects

  • If your child gets a skin rash, stop giving the medicine and call your child's doctor.
  • For the “metal” taste, your child can chew sugarless gum or suck on sugarless candy.
  • For nausea, give the medicine with food.
  • There is nothing wrong if the urine turns brown.

When to Call for Emergency Help

Call for emergency help if your child has any of these signs of an allergic reaction: trouble breathing, swelling of the tongue, swelling of hands, feet or ankles.

When to Call the Doctor

Call your child's doctor if your child has:

  • Numbness or tingling, unsteady walk, shaky hands, or dizziness.
  • Nausea or vomiting that will not go away.
  • Skin rash, hives, redness or itching.
  • Irritated mouth or “furry” tongue.
  • Any side effects that continue or keep bothering your child.


  • Ask the pharmacist for 2 labeled bottles if your child’s care provider or school nurse will be giving this medicine.
  • Get this prescription refilled at least 3 days before the last dose is given. This is very important.
  • Some pharmacies may not have this medicine in a liquid form. Please ask your child’s nurse to call your pharmacy before you leave the hospital to see if they have this medicine or if they can order it or make it for you. You may also have the prescription filled at the Nationwide Children’s Hospital Pharmacy.
  • Ask your nurse for Helping Hands HH-I-172, Giardia, and HH-I-179, Inflammatory Bowel Disease (IBD).

Other Advice about the Medicine

  • Tell your child's doctor and pharmacist if your child has a strange or allergic reaction to any medicine.
  • If you carry medicine in your purse, keep it in its childproof bottle and keep your purse out of the reach of children.
  • Bring all your child's medicines with you in the original bottles whenever your child sees a doctor, goes to an emergency room, or is admitted to the hospital. This helps doctors who may not know your child.
  • Learn the name, spelling and dose of this medicine. Also, teach your child if he is old enough. You will need to know this information when you call your doctor or pharmacist.
  • If your child takes too much of this medicine, or if someone else takes this medicine, first call the Central Ohio Poison Center at 1-800-222-1222 (TTY 614-228-2272). They will tell you what to do.
  • Do not stop giving this medicine or change the amount given without first talking with your child's doctor or pharmacist. The illness may come back if the antibiotic is not finished.  
  • The doctor has prescribed this medicine for your child only. Do not give it to anyone else.
  • Tell your child's teacher, school nurse, coach, babysitter and others that your child is taking this medicine and what side effects to watch for.
  • Your child's school will need a note from you and from the doctor if the medicine is to be given at school by the school nurse.

Follow-Up Visits

Write down all your questions as you think of them. Bring this list with you when you see the doctor. Be sure to call your doctor if you can't keep the appointment.

If you have any questions, be sure to ask your child’s doctor, nurse, or pharmacist.

Metronidazole (Flagyl®, Flagyl ER®) – GI (PDF) 

HH-V-39 1/90 Revised 10/15  Copyright 1990, Nationwide Children’s Hospital