What is metronidazole?

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Generic Name: Metronidazole Brand Name(s): Generics only. No brands available.

Know the basics

What is metronidazole used for?

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

This antibiotic only treats bacterial and protozoal infections. 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 can also be used in combination with anti-ulcer medications to treat certain types of stomach ulcers.

How should I take metronidazole?

Metronidazole may be taken with food or a full glass of water or milk to prevent stomach upset. Dosage is based on your medical condition, the type of infection being treated, and your response to therapy.

Antibiotics work best when the amount of medicine in your body is kept at a constant level. Therefore, take this drug at evenly spaced intervals.

Continue to take metronidazole until the full prescribed amount is finished, even if symptoms disappear after a few days. Stopping the metronidazole too early may allow bacteria/protozoa to continue to grow, which may result in a relapse of the infection.

Inform your doctor if your condition persists or worsens.

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 metronidazole in the bathroom or the freezer. There may be different brands of metronidazole that may have different storage needs. 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 metronidazole 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. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using metronidazole?

Before taking metronidazole,

  • Tell your doctor and pharmacist if you are allergic to metronidazole or any other drugs.
  • Tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially anticoagulants (‘blood thinners’) such as warfarin (coumadin), astemizole (hismanal), disulfiram (antabuse), lithium (lithobid), phenobarbital, phenytoin (dilantin), and vitamins.
  • Tell your doctor if you have or have ever had blood, kidney, or liver disease or crohn’s disease.
  • Tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking metronidazole, call your doctor.
  • Know that you should not drink alcohol while taking this drug. Alcohol may cause an upset stomach, vomiting, stomach cramps, headaches, sweating, and flushing (redness of the face).
  • Plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen. Metronidazole may make your skin sensitive to sunlight.

Is it safe to take metronidazole during pregnancy or breast-feeding?

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 metronidazole. 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

Know the side effects

What are the side effects of metronidazole?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor if you have severe stinging or burning when you apply metronidazole topical.

Less serious side effects may include:

  • Mild burning or stinging when the metronidazole is applied;
  • 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; or
  • Metallic taste in your mouth.

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

Know the interactions

What drugs may interact with metronidazole?

Metronidazole 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.

  • Cimetidine (Tagamet);
  • Seizure metronidazole such as 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 metronidazole?

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?

Metronidazole 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. , especially:

  • Blood or bone marrow problems, or history of;
  • Brain disease (eg, aseptic meningitis, encephalopathy);
  • Leukopenia (low white blood cells), history of;
  • Optic neuropathy (eye disease with vision changes), history of;
  • Oral thrush (Candida infection);
  • Peripheral neuropathy (nerve disease with pain, numbness, or tingling), history of or
  • Seizures, history of;
  • Vaginal yeast infection (Candida infection)—Use with caution. May make these conditions worse.
  • Kidney disease, end-stage;
  • Liver disease, severe—Use with caution. The effects may be increased because of slower removal of the medicine from the body.

Understand the 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 of metronidazole for an adult?

Usual Adult Dose for Bacterial Infection: Serious anaerobic infections:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Amebiasis:

  • Acute intestinal amebiasis (acute amebic dysentery): 750 mg orally 3 times a day for 5 to 10 days;
  • Amebic liver abscess: 500 to 750 mg orally 3 times a day for 5 to 10 days;

Usual Adult Dose for Pseudomembranous Colitis:

  • Mild to moderate Clostridium difficile infection (CDI): 500 mg orally 3 times a day;
  • Severe, complicated CDI: 500 mg Intravenous injection every 8 hours;

Usual Adult Dose for Surgical Prophylaxis

  • Initial preoperative dose: 15 mg/kg intravenous infused over 30 to 60 minutes and completed about 1 hour before surgery;
  • Intraoperative/postoperative dose: 7.5 mg/kg intravenous infused over 30 to 60 minutes at 6 and 12 hours after the initial dose;

Usual Adult Dose for Trichomoniasis

  • 1-day regimen: 2 g orally as a single dose (or as 1 g twice on the same day).
  • 7-day regimen:
  • Tablets: 250 mg orally 3 times a day for 7 consecutive days
  • Capsules: 375 mg orally twice a day for 7 consecutive days

Usual Adult Dose for Helicobacter pylori Infection:

  • Bismuth quadruple therapy: 250 mg orally 4 times a day;
  • Clarithromycin-based triple therapy: 500 mg orally twice a day;
  • Duration of therapy: 10 to 14 days;

Usual Adult Dose for Pelvic Inflammatory Disease, intravenous administration:

  • Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Bacterial Vaginosis: Extended-release tablets: 750 mg orally once a day for 7 consecutive days

Usual Adult Dose for Aspiration Pneumonia:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Bacteremia:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Meningitis:

  • IV: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Diverticulitis:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Intraabdominal Infection:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Peritonitis:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Endocarditis:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Joint Infection:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection ;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Osteomyelitis:  

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Pneumonia:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Skin or Soft Tissue Infection:

  • Intravenous injection: Loading dose: 15 mg/kg Intravenous injection;
  • Oral: 7.5 mg/kg orally every 6 hours;

Usual Adult Dose for Giardiasis: Some experts recommend: 250 mg orally 3 times a day for 5 to 7 days

Usual Adult Dose for STD Prophylaxis: CDC recommendations:
Prophylaxis after sexual assault: 2 g orally as a single dose.

Usual Adult Dose for Nongonococcal Urethritis: CDC recommendations:
Recurrent or persistent urethritis: 2 g orally as a single dose

Usual Adult Dose for Balantidium coli: Some experts recommend: 500 to 750 mg orally 3 times a day for 5 days.

Usual Adult Dose for Dientamoeba fragilis: Some experts recommend: 500 to 750 mg orally 3 times a day for 10 days

What is the dose of metronidazole for a child?

Usual Pediatric Dose for Bacterial Infection:

  • Neonates :
  • 7 days or less, 2000 g or less: 7.5 mg/kg IV every 24 to 48 hours;
  • 7 days or less, greater than 2000 g: 15 mg/kg IV every 24 hours;
  • 8 to 28 days, 2000 g or less: 15 mg/kg IV every 24 hours;
  • 8 to 28 days, greater than 2000 g: 15 mg/kg IV every 12 hours;
  • 1 month or older:
    • Intravenous injection: 22.5 to 40 mg/kg/day Intravenous injection in 3 divided doses;
    • Oral: 30 to 50 mg/kg/day orally in 3 divided doses;

Usual Pediatric Dose for Amebiasis: 35 to 50 mg/kg/day orally in 3 divided doses for 10 days.

Usual Pediatric Dose for Pseudomembranous Colitis: AAP recommendations:
Children and adolescents: 30 mg/kg/day orally in 4 divided doses.

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

Usual Pediatric Dose for Bacterial Vaginosis: Children less than 45 kg with prepubertal vaginitis (STI-related): 15 mg/kg/day orally in 2 divided doses for 7 days
Adolescent vulvovaginitis: 500 mg orally twice a day for 7 days.

Usual Pediatric Dose for Giardiasis: Some experts (includes AAP) recommend: 15 mg/kg/day orally in 3 divided doses for 5 to 7 days.

Usual Pediatric Dose for STD Prophylaxis: Prophylaxis after Sexual Assault

AAP recommendations for preadolescent children:

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

Usual Pediatric Dose for Balantidium coli: Some experts (includes AAP) recommend: 35 to 50 mg/kg/day orally in 3 divided doses for 5 days.

Usual Pediatric Dose for Dientamoeba fragilis: Some experts (includes AAP) recommend: 35 to 50 mg/kg/day orally in 3 divided doses for 10 days.

How is metronidazole available?

Metronidazole is available in the following dosage forms and strengths:

  • Tablet, Oral: 250 mg, 500 mg.

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 your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of metronidazole, 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.

msBahasa Malaysia

Review Date: May 30, 2016 | Last Modified: January 4, 2017

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