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Metronidazole (Antibiotic, Antiparasitic agent)

Uses|Precautions & warnings|Side effects|Interactions|Dosage

Metronidazole is used to treat variety of infections. It belongs to a class of antibiotics known as nitroimidazole. It works by stopping the growth of bacteria and protozoa.

It will not work for viral infections (e.g., common cold, flu). Unnecessary use or overuse of any antibiotic can lead to its decreased effectiveness.

metronidazole

Uses

What is metronidazole used for?

Metronidazole can also be used in combination with anti-ulcer medicines to treat certain types of stomach ulcers.

How should I take metronidazole?

Oral tablets should be taken with food. Swallow the tablet whole with a glass of water. Do not crush or chew the tablet.

Oral suspensions should be taken on an empty stomach, ideally at least 1 hour before meals.

For suppositories, carefully read the directions on the packaging. Gently insert the suppository into the rectum or vagina, as directed. Laying on your side or squatting may make insertion easier.

For topical products, apply an appropriate amount to the affected area. Wash your hands before and after applying the product.

For intravenous (IV) solutions, the dose should be administered by a doctor, nurse, or other certified professional.

How do I store metronidazole?

Metronidazole is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer. There are different brands of metronidazole which may have different storage needs. That is why it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. If necessary, consult a pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using metronidazole?

Before using metronidazole, tell your doctor if you have/had:

  • An allergic reaction to metronidazole before
  • Allergic reactions to any other medicines, foods, dyes, preservatives, or animals
  • Any other health conditions

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using metronidazole during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking any drug. Metronidazole is pregnancy risk category B, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effects

What side effects can occur from metronidazole?

As taking others medicines, taking this drug can cause some side effects. Most of them are rarely occurring and do not need any supplementary treatment. However, it is always important for you to consult your doctor if you have any problem after taking this medicine.

Some of side effects are listed below:

  • Mild burning or stinging
  • Numbness or tingly feeling in your hands or feet
  • Cough
  • Stuffy nose
  • Sore throat
  • Cold symptoms
  • Vaginal itching or discharge
  • Headache
  • Dry, scaly, or itchy skin
  • Nausea
  • Metallic taste in your mouth

Not everyone experiences these side effects. Additionally, there may be other side effects not listed above. If you have any concerns about a side effect, please consult your doctor or pharmacist.

Interactions

What drugs may interact with metronidazole?

This drug may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products may interact with this drug, including:

  • Cimetidine (Tagamet)
  • Phenytoin (Dilantin) or phenobarbital (Luminal, Solfoton)
  • A blood thinner such as warfarin (Coumadin, Jantoven)
  • Lithium (Lithobid, Eskalith, others)
  • Disulfiram (Antabuse)

Does food or alcohol interact with metronidzaole?

Metronidazole may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with metronidazole?

This drug may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.

These health conditions are:

  • Blood or bone marrow problems
  • Brain disease (e.g., aseptic meningitis, encephalopathy)
  • Leukopenia (low white blood cells)
  • Optic neuropathy (eye disease with vision changes)
  • Oral thrush (Candida infection)
  • Peripheral neuropathy (nerve disease with pain, numbness, or tingling)
  • Seizures
  • Vaginal yeast infection (Candida infection)
  • End-stage of kidney disease
  • Severe liver disease

Dosage

The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using metronidazole.

What is the dose for an adult?

Consult your doctor for information about the exact dose for you.

Bacterial infection (Serious anaerobic infections)

The recommended dose is 7.5 mg/kg orally every 6 hours.

Amebiasis:

Acute intestinal amebiasis (acute amebic dysentery): the recommended dose is 750 mg orally 3 times a day for 5 to 10 days.

Amebic liver abscess: the recommended dose is 500 to 750 mg orally 3 times a day for 5 to 10 days.

Pseudomembranous colitis:

Mild to moderate clostridium difficile infection (CDI): the recommended dose is 500 mg orally 3 times a day.

Surgical prophylaxis

Initial preoperative dose: the recommended dose is 15 mg/kg intravenous infused over 30 to 60 minutes and completed about 1 hour before surgery.

Intraoperative/postoperative dose: the recommended dose is 7.5 mg/kg intravenous infused over 30 to 60 minutes at 6 and 12 hours after the initial dose.

Trichomoniasis

1-day regimen: the recommended dose is 2 g orally as a single dose (or as 1 g twice on the same day).

7-day regimen: the recommended dose is 250 mg orally 3 times a day for 7 consecutive days.

Helicobacter pylori infection:

Bismuth quadruple therapy: the recommended dose is 250 mg orally 4 times a day.

Clarithromycin-based triple therapy: the recommended dose is 500 mg orally twice a day.

Duration of therapy is 10 to 14 days.

Pelvic inflammatory disease, intravenous administration:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Bacterial vaginosis:

Extended-release tablets: the recommended dose is 750 mg orally once a day for 7 consecutive days.

Aspiration Pneumonia:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Bacteremia:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Meningitis:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Diverticulitis:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Intraabdominal infection:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Peritonitis:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Endocarditis:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Joint infection:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Osteomyelitis:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Pneumonia:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Skin or soft tissue infection:

The recommended dose is 7.5 mg/kg orally every 6 hours.

Giardiasis:

The recommended dose is 250 mg orally 3 times a day for 5 to 7 days.

STD prophylaxis:

Prophylaxis after sexual assault: the recommended dose is 2 g orally as a single dose.

Nongonococcal urethritis:

Recurrent or persistent urethritis: the recommended dose is 2 g orally as a single dose.

Balantidium coli:

The recommended dose is 500 to 750 mg orally 3 times a day for 5 days.

Dientamoeba fragilis:

The recommended dose is 500 to 750 mg orally 3 times a day for 10 days.

What is the dose for a child?

Consult your doctor for information about the dose of metronidazole.

Recommended doses in some cases are listed below:

1 month or older: the recommended dose is 30 to 50 mg/kg/day orally in 3 divided doses.

Amebiasis:

The recommended dose is 35 to 50 mg/kg/day orally in 3 divided doses for 10 days.

Pseudomembranous colitis:

Children and adolescents: the recommended dose is 30 mg/kg/day orally in 4 divided doses.

Trichomoniasis:

Children less than 45 kg with prepubertal vaginitis (sexually transmitted infection [STI]-related): the recommended dose is 15 mg/kg/day orally in 3 divided doses for 7 days.

Bacterial vaginosis:

Children less than 45 kg with prepubertal vaginitis (STI-related): the recommended dose is 15 mg/kg/day orally in 2 divided doses for 7 days.

Adolescent vulvovaginitis: the recommended dose is 500 mg orally twice a day for 7 days.

Giardiasis:

The recommended dose is 15 mg/kg/day orally in 3 divided doses for 5 to 7 days.

STD prophylaxis (prophylaxis after sexual assault)

For preadolescent children

Less than 45 kg: the recommended dose is 15 mg/kg/day orally in 3 divided doses for 7 days.

Balantidium coli:

The recommended dose is 35 to 50 mg/kg/day orally in 3 divided doses for 5 days.

Dientamoeba fragilis:

The recommended dose is 35 to 50 mg/kg/day orally in 3 divided doses for 10 days.

How is metronidazole available?

Metronidazole is already available in the following dosage forms:

  • Oral tablet
  • Oral suspension
  • Topical gel/cream
  • Vaginal suppository
  • Intravenous injectable solution

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Metronidazole https://www.mims.com/philippines/drug/info/metronidazole?mtype=generic Accessed May 26, 2021

Metronidazole https://www.nhs.uk/medicines/metronidazole/ Accessed May 26, 2021

Metronidazole (Vaginal Route) https://www.mayoclinic.org/drugs-supplements/metronidazole-vaginal-route/proper-use/drg-20064738 Accessed May 26, 2021

Metronidazole (Topical Route) https://www.mayoclinic.org/drugs-supplements/metronidazole-topical-route/proper-use/drg-20064727?p=1 Accessed May 26, 2021

Flagyl https://www.mims.com/philippines/drug/info/flagyl Accessed May 26, 2021

Metronidazole https://www.ncbi.nlm.nih.gov/books/NBK539728/ Accessed May 26, 2021

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Written by Stephanie Nicole Nera, RPh, PharmD on May 03, 2020
Medically reviewed by Stephanie Nicole Nera, RPh, PharmD
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