1. Introduction
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent used to treat bacterial and parasitic infections. It is effective against anaerobic bacteria and certain protozoa. Commonly prescribed for infections like bacterial vaginosis, pelvic inflammatory disease, and certain gastrointestinal conditions, Metronidazole works by disrupting DNA synthesis in microorganisms, leading to cell death.
2. Indications
- Bacterial vaginosis
- Pelvic inflammatory disease
- Anaerobic bacterial infections (e.g., intra-abdominal infections, skin infections, sepsis)
- Amoebiasis (e.g., Entamoeba histolytica infections)
- Giardiasis (Giardia lamblia infection)
- Trichomoniasis
- Helicobacter pylori infection (as part of combination therapy)
- Clostridium difficile-associated diarrhoea
3. Dosage
Adults:
- Bacterial infections (general): 500 mg every 8 hours for 7–10 days.
- Bacterial vaginosis: 500 mg twice daily for 7 days or 2 g as a single dose.
- Trichomoniasis: 2 g as a single dose or 500 mg twice daily for 7 days.
- Amoebiasis: 500–750 mg three times daily for 5–10 days.
- Helicobacter pylori (as part of triple therapy): 500 mg twice daily for 7–14 days.
Children:
- Anaerobic infections: 7.5 mg/kg every 8 hours (maximum 500 mg per dose).
- Amoebiasis: 35–50 mg/kg/day in 3 divided doses for 10 days.
- Giardiasis: 15 mg/kg/day in 2–3 divided doses for 5–7 days (maximum 2 g/day).
4. Administration
- Take oral tablets with food or a full glass of water to reduce stomach upset.
- Extended-release formulations should be taken on an empty stomach (1 hour before or 2 hours after meals).
- For intravenous use, administer slowly to prevent irritation.
5. Forms Available
- Tablets: 250 mg, 500 mg
- Oral suspension: 200 mg/5 mL
- Intravenous solution: 500 mg/100 mL
- Vaginal gel: 0.75%
- Topical gel/cream: 0.75%, 1%
6. Side Effects
6.1 Common Side Effects:
- Nausea
- Metallic taste
- Abdominal pain
- Diarrhoea
6.2 Less Common Side Effects:
- Dizziness
- Headache
- Dry mouth
6.3 Rare but Serious Side Effects:
- Peripheral neuropathy (prolonged or high-dose use)
- Seizures
- Stevens-Johnson syndrome
- Hepatotoxicity
7. Warnings
- Alcohol Use: Avoid alcohol during treatment and for at least 48 hours after completing therapy to prevent disulfiram-like reactions (e.g., flushing, nausea, vomiting).
- CNS Effects: Use cautiously in patients with neurological conditions as it may cause seizures or neuropathy.
- Hepatotoxicity: Monitor liver function in patients with hepatic impairment.
8. Precautions
- Use with caution in patients with blood dyscrasias as Metronidazole may cause transient leukopenia.
- Avoid prolonged use due to the risk of neuropathy.
- Dose adjustments may be needed in severe hepatic impairment.
9. Interactions
- Alcohol: Causes disulfiram-like reactions.
- Warfarin: Prolongs INR, increasing the risk of bleeding.
- Phenytoin or Phenobarbital: Decreases Metronidazole levels, reducing effectiveness.
- Lithium: Increases lithium toxicity risk.
- CYP3A4 inhibitors (e.g., ketoconazole): May increase Metronidazole levels.
10. Monitoring Parameters
- Monitor for therapeutic response (symptom resolution).
- Liver function tests for prolonged use or in hepatic impairment.
- Neurological symptoms (e.g., tingling, numbness, or seizures) during high-dose or long-term therapy.
11. Use in Children
- Safe and effective for certain infections, such as amoebiasis and giardiasis, under medical supervision.
- Dose must be carefully adjusted by weight.
12. Use in Pregnancy
- Generally avoided in the first trimester unless absolutely necessary.
- Can be used in the second and third trimesters for certain conditions under medical supervision.
13. Use in Elderly
- Generally well-tolerated in elderly patients; dose adjustments may be required for hepatic or renal impairment.
14. Use in Kidney Disease
- Use with caution; no specific dose adjustment is required in mild to moderate renal impairment.
- For severe renal impairment or haemodialysis, adjust dose or extend dosing intervals.
15. Use in Liver Disease
- Reduce dosage in severe hepatic impairment (e.g., Child-Pugh C classification).
16. Patient Counselling Points
- Take the medication as directed; do not skip doses.
- Avoid alcohol during and for 48 hours after the last dose to prevent adverse reactions.
- Report any unusual symptoms, such as numbness, tingling, or severe diarrhoea, to your doctor.
- If using the vaginal gel, follow application instructions carefully and avoid intercourse during treatment.
- Store the medication at room temperature and out of reach of children.
17. Table of Brand Names, Manufacturer, and Prices in USD
Brand Name | Manufacturer | Strength/Dosage Form | Price (USD) |
---|---|---|---|
Flagyl | Pfizer | 500 mg Tablet | $10 (10 tablets) |
Metrogel | Galderma | 0.75% Vaginal Gel | $35 (45 g tube) |
Noritate | Meda | 1% Topical Cream | $40 (45 g tube) |
Generic Metronidazole | Various | 500 mg IV Solution | $15 (1 vial) |
18. 15 FAQs (Frequently Asked Questions)
1. What is Metronidazole?
Metronidazole is an antibiotic and antiprotozoal medication used to treat bacterial and parasitic infections.
2. How does Metronidazole work?
It disrupts the DNA synthesis of anaerobic bacteria and protozoa, leading to cell death.
3. What is the usual dose for adults?
For most infections, 500 mg every 8 hours for 7–10 days is common.
4. Can Metronidazole be taken during pregnancy?
It is avoided during the first trimester but can be used later in pregnancy under medical supervision.
5. Can Metronidazole be used while breastfeeding?
Use cautiously, as it passes into breast milk. Short-term therapy may be safe, but consult a doctor.
6. What are the common side effects of Metronidazole?
Nausea, metallic taste, abdominal pain, and diarrhoea.
7. Can Metronidazole interact with alcohol?
Yes, it can cause severe reactions such as nausea, vomiting, and flushing. Avoid alcohol during treatment and for 48 hours after the last dose.
8. How long does it take for Metronidazole to work?
It usually starts working within 1–2 days, but complete the prescribed course for full effectiveness.
9. Can Metronidazole cause neuropathy?
Yes, prolonged use or high doses can cause peripheral neuropathy.
10. Is Metronidazole effective for C. difficile infections?
Yes, it is used to treat mild to moderate C. difficile infections.
11. How should Metronidazole be stored?
Store at room temperature, away from moisture and light.
12. Can children take Metronidazole?
Yes, it is safe for children when prescribed for specific infections like amoebiasis or giardiasis.
13. Can Metronidazole cause liver damage?
In rare cases, it may cause hepatotoxicity, especially in patients with pre-existing liver conditions.
14. What should I do if I miss a dose?
Take the missed dose as soon as you remember, unless it’s close to the next dose. Do not double the dose.
15. Is Metronidazole available over the counter?
No, Metronidazole is a prescription-only medication.