Introduction


Metronidazole is a powerful medication with a broad spectrum of activity against parasites and bacteria. However, it’s crucial to consult a healthcare professional to determine the appropriate indication and dosage for your specific condition, considering potential side effects and interactions.

Indication of Metronidazole

Metronidazole is indicating for the treatment of

  • Pneumonia,
  • Giardiasis,
  • Peptic ulcer disease,
  • peritonitis,
  • H. pylori infection,
  • Rosacea,
  • Septicemia,
  • Endometritis,
  • Aspiration pneumonia,
  • Lung abscess,
  • empyema,
  • Bone and joint Infection,
  • Surgical prophylaxis,
  • Amoebiasis,
  • Bacterial vaginosis,
  • Balantidiasis, Blastocystis hominis infection,
  • Trichomoniasis,
  • Acute dental infections,
  • Acute necrotising ulcerative gingivitis,
  • Anaerobic bacterial infection,
  • Antibiotic-associated colitis,
  • Fungating tumours,
  • Leg ulcers and pressure sores,
  • Diverticulitis,
  • Diabetic foot ulcer,
  • Meningitis and brain abscesses,
  • Endocarditis.

Doses of Metronidazole

Adult dose

Child: PO 30 – 50 MG/ KG/ day q8hour

Amoebiasis
Adult: 800 mg tid for 5 days ( intestinal infection); 5-10 days (extra-intestinal infection). Max: 2.4 gram/day.

Trichomoniasis
Adult: 2g as a single dose, 200 mg tid for 7 days or 400 mg bid for 5 – 7 days. Sexual partners should also be treated. Repeat treatment 4- 6 weeks between courses as necessary.

Giardiasis
Adult: 2 gram once daily for 3 days, 400 mg tid for 5 days or 500 mg bid for 7 – 10 days.

Bacterial vaginosis
Adult: 2 gram as a single dose or 400 mg bid for 5 – 7 days.

Acute necrotising ulcerative gingivitis
Adult: 200 mg tid for 3 days.

Anaerobic bacterial infections
Adult: Initially 800 mg followed by 400 mg 8 hourly. Alternatively, 7.5 mg/kg 6-8 hourly. Max: 4 gram/ day. Duration of treatment is usually for 7 days depending on the severity of infection.

Prophylaxis of postoperative anaerobic bacterial infections
Adult: 400 mg 8 hourly 24 hour prior to surgery followed by post-op IV or rectal admin until oral therapy is possible.

Eradication of H. Pylori associated with peptic ulcer disease
Adult: 400 mg bid in combination w/ another antibacterial and a PPI or 400 mg tid. If given w/ omeprazole and amoxicillin. Initial treatment is given for 1 week.

Leg ulcers and pressure sores
Adult: 400 mg tid for 7 days.

Acute dental infections
Adult: 200 mg tid for 3- 7 days.

Intravenous

Child: IV 22.5 – 40 mg/kg/day Q 8 hour.

Anaerobic bacterial infections
Adult: 500 mg infused as 100 ml of a 5 mg/ml solution at 5 ml/min 8 hourly. Alternatively, 15mg/kg infused over 1 hour, followed by 7.5 mg/kg infused over 1 hour 6 hourly. Max: 4 g/day. Substitute oral therapy as soon as possible.

Prophylaxis of postoperative anaerobic bacterial infections
Adult: 500 mg shortly before operation and repeated 8 hourly. Alternatively, 15 mg/kg infused over 30 – 60 min and completed approx 1 hour before surgery, followed by 7.5 mg/kg infused over 30 – 60 min at 6 and 12 after the initial dose.

Hepatic impairment: Severe: ⅓ of usual dose once daily.

Child dose

Oral Amoebiasis
Child: 1-3 years 100-200 mg tid

3-7 years 100-200 mg 4 times daily
7-10 years 200-400 mg tid. Doses are given for 5-10 days.

Trichomoniasis
Child: 1-10 years 40 mg/kg as a single dose or 15-30 mg/kg daily in 2-3 divided doses for 7 days. Max: 2 g/dose.

Giardiasis
Child: 1-3 years 500 mg once daily;

3-7 years 600-800 mg once daily;
7-10 years 1 gram once daily. Doses are given for 3 days.

Acute necrotising ulcerative gingivitis
Child: 1-3 years 50 mg tid;

3-7 years 100mg bid;
7-10 years 100 mg tid. Doses are given for 3 days.

Anaerobic bacterial infections
Child: <8 weeks 7.5 mg/kg 12 hourly or 15 mg/kg once daily.
8 weeks to 12 years 7.5 mg/kg 8 hourly or 20-30 mg/kg once daily. Duration of treatment is usually for 7 days depending on the severity of infection.

Prophylaxis of postoperative anaerobic bacterial infections
Child: <40 weeks 10 mg/kg as a single dose before surgery;
<12 years 20-30 mg/kg as a single dose 1-2 hour before surgery.

Intravenous

Anaerobic bacterial infections
Child: 7.5 mg/kg 8 hourly.

Administration

Metronidazole is typically administered orally, either with or without food, as directed by a healthcare professional.

contraindication of Metronidazole

Allergies:

If you have a known allergy to metronidazole or other nitroimidazole antibiotics, then metronidazole is contraindicate. This can cause allergic reactions ranging from mild rash to life-threatening anaphylaxis.


Cockayne syndrome:

Metronidazole is contraindicated in people with Cockayne syndrome, a rare genetic disorder that affects growth and development. Metronidazole can cause severe liver damage in people with this condition.


Disulfiram:

Metronidazole should not be used if you are taking disulfiram (Antabuse), a medication used to treat alcohol dependence. Taking these two medications together can cause a severe reaction with symptoms like nausea, vomiting, flushing, and cramps.


First trimester of pregnancy:

Metronidazole is generally not recommended for use in the first trimester of pregnancy, as there is some evidence that it may increase the risk of birth defects.


Severe liver impairment:

Metronidazole should be used with caution and at a reduced dose in people with severe liver impairment, as it can worsen liver function.


Alcohol:

While not technically a contraindication, it is important to avoid alcohol while taking metronidazole and for at least 3 days after finishing your course. Drinking alcohol during this time can cause a disulfiram-like reaction with unpleasant side effects like nausea, vomiting, flushing, and cramps.

Side effect of Metronidazole

Get emergency medical help if you have signs of an allergic reaction to metronidazole (hives, itching, warmth, or tingling; fever, joint pain; dry mouth, dry vagina; stuffy nose, difficulty breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Metronidazole may cause serious side effects including:

Nervous system problems, including brain disorder (encephalopathy), inflammation of the brain and spinal cord membranes (aseptic meningitis), numbness or tingling in the hands or feet (peripheral neuropathy), and seizures (convulsions). Tell your healthcare provider right away if you have any nervous system problems while taking metronidazole
Worsening yeast infection (candidiasis) symptoms in people with a known yeast infection or a yeast infection they were not aware of
Low white blood cell count (leukopenia) in people with a history of blood problems. This can affect how well the body fights infection.

The most common side effects of metronidazole include

Diarrhea
Nausea
Headache
Pain in the upper abdomen and abdominal cramping
Vomiting
Weight loss
Constipation.

Other side effects of metronidazole may include allergic reactions:

Such as itching, hives (urticaria), flushing of the skin, red skin rash that can be widespread, blisters and separation of skin layers, nasal congestion, dryness of the mouth and vagina, and fever.

Abnormal heart rhythms (QT prolongation) may also occur. Metronidazole can cause life-threatening liver problems in people with Cockayne syndrome. If you have this condition, stop taking this medicine and contact your doctor if you have signs of liver failure–nausea, stomach pain (upper right side), dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).

These are not all the possible side effects of metronidazole. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

precautions and warnings of Metronidazole

Precautions:

  • Inform your doctor about any allergies: Tell your doctor if you have any allergies to metronidazole, other antibiotics (like tinidazole), or any other medications.
  • Disclose existing medical conditions: Share your medical history, particularly if you have liver disease, kidney disease, certain blood disorders (low blood cell counts), or a rare genetic disorder called Cockayne syndrome.
  • Pregnancy and breastfeeding: Discuss metronidazole use with your doctor if you’re pregnant or breastfeeding, as it can potentially harm the baby.
  • Alcohol and propylene glycol: Avoid alcohol and products containing propylene glycol while taking metronidazole and for at least 3 days after finishing. This combination can cause severe discomfort like nausea, vomiting, and cramps.
  • Marijuana and dizziness: Be cautious when using marijuana while on metronidazole, as both can worsen dizziness. Avoid activities requiring alertness until you know how the medication affects you.
  • Live bacterial vaccines: Taking metronidazole might interfere with the effectiveness of live bacterial vaccines like typhoid vaccine.

Warnings:

  • Central nervous system effects: In rare cases, metronidazole can affect the nervous system, causing confusion, seizures, numbness, tingling, or vision problems. If you experience any of these symptoms, seek immediate medical attention.
  • Allergic reactions: While rare, serious allergic reactions like rashes, swelling, and breathing difficulties can occur. Discontinue use and seek medical help if you suspect an allergic reaction.
  • Yeast infections: Prolonged or repeated use of metronidazole can increase the risk of oral thrush or vaginal yeast infections. Contact your doctor if you notice white patches in your mouth, changes in vaginal discharge, or other new symptoms.
  • Skin reactions: Severe skin reactions, including blistering, peeling, and sores, can occur in rare cases. Seek immediate medical attention if you experience any such reactions.

pregnancy and lactation

Pregnancy


There are no adequate and well-controled studies of in pregnant women. There are publishing data from case-control studies,cohort studies and 2 meta-analyses that include more than 5000 Pregnant women who used metronidazole during pregnancy. Many studies included first trimester exposures; one study showed increased risk of cleft lip, with or without cleft palate, in infant exposed to Metronidazole in utero. However, these fidings were not confirmed.

Metronidazole crosses placental barrier and its effects on human fetal organogenesis are not known. Reproduction studies have been performed in rats, rabbits and mice at doses similar to maximum recommended daily dose based on body surface area comparisons. There was no evidence of harm to fetus due to metronidazole. Health Care provider should carefully consider Potential X and benefits for each specific patient before prescribing therapy.

Lactation

Metronidazole is present in human milk at concentrations similar to maternal serum levels and Infant serum levels can be close to or comparable to infant therapeutic levels.
Because of Potential for tumorigenicity shown for metronidazole in mouse and rat studies. A decision should be made whether to discontinue nursing or to discontinue drug, taking into account importance of drug to mother. Alternatively, a nursing mother may choose to Pump and discard human milk for duration of metronidazole therapy and for 24 hours after therapy ends and feed her infant stored human Milk or formula.

therapeutic class

Anti-diarrhoeal Antiprotozoal, Amoebicides.

Mode of action

The exact mode of action of metronidazole has not been fully established. However, it is possible that an intermediate in the reduction of metronidazole which is only made by anaerobic bacteria and protozoa, binds deoxyribonucleic acid and electron-transport proteins of organisms, blocking nucleic acid synthesis. After administration, metronidazole enters cells by passive diffusion. Following this, ferredoxin or flavodoxin reduce its nitro group to nitro radicals. The redox potential of the electron transport portions of anaerobic or microaerophilic microorganisms renders metronidazole selective to these organisms, which cause nitro group reduction, leading to the production of toxic metabolites. These include N-(2-hydroxyethyl) oxamic acid and acetamide, which may damage DNA of replicating organisms.

Interaction

Concurrent use w/ disulfiram may produce psychotic reactions. May potentiate the effect of oral anticoagulants. May increase risk of lithium toxicity. Also may reduce the renal clearance resulting to increased toxicity of 5-fluorouracil. May increase serum levels of ciclosporin. May increase plasma levels of busulfan resulting to severe busulfan toxicity. Enhanced metabolism w/ phenobarbital and phenytion resulting to decreased serum concentrations.

Popular FAQ of Metronidazole

How quickly does Metronidazole work?

The onset of action varies depending on the specific infection being treated. Consult your healthcare provider for more information.

What happens if you drink alcohol with metronidazole?

Drinking alcohol while taking metronidazole is not recommended. Because the combination of metronidazole and alcohol can cause a reaction (often referred to as a disulfiram-like reaction) in some people. Symptoms may include flushing, headaches, nausea, vomiting, and stomach cramps. There has been one reported death associated with this reaction.

Are there any dietary restrictions with Metronidazole?

While there are no strict dietary restrictions, it is recommended to take Metronidazole with food to minimize stomach upset.

Can Metronidazole be used to treat viral infections?

No, Metronidazole is effective against certain bacteria and parasites, not viruses.

Are there any long-term side effects of Metronidazole?

Long-term side effects are rare, but any concerns should be discussed with a healthcare professional.

Can you have sex while taking metronidazole?

If you are taking oral metronidazole or using metronidazole gel for an infection that is linked with sexual activity. Such as trichomoniasis, pelvic inflammatory disease, or bacterial vaginosis you should not have sex for 7 days after single-dose therapy (or until you have completed the 7-day treatment regimen) and your symptoms have resolved. This will help reduce the risk of reinfection. If your sexual partners are also being treated. Then abstain from sexual intercourse until they have finished treatment.

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