Flagyl (Metronidazole)
Also sold as: Flagyl, Metrogyl, Metron, Aristogyl
Pregnancy
Cat B
Lactation
Caution
Schedule
H
Forms
Tablet 200/400mg +3
Indications
- Anaerobic infections
- C. difficile colitis (mild-moderate)
- Bacterial vaginosis
- Trichomoniasis
- Amoebiasis
- Giardiasis
- H. pylori (in regimens)
- Dental infections
Adult Dosing
Anaerobic infections
400 mg PO TDS
7-14 days
BV / Trichomoniasis
500 mg PO BD × 7 days OR 2 g single dose
Amoebiasis (intestinal)
750 mg PO TDS
5-10 days
Giardiasis
250 mg PO TDS
5-7 days
C. difficile (mild)
500 mg PO TDS
10-14 days (vancomycin preferred per IDSA 2021)
Pediatric Dosing
Giardiasis: 15 mg/kg/day TDS × 5 days
Renal Dose Adjustment
| CrCl / eGFR | Dose Adjustment |
|---|---|
| CrCl > 10 mL/min | No adjustment |
| CrCl < 10 mL/min | Consider 50% dose reduction |
Hepatic Adjustment
Reduce dose by 50% in severe hepatic impairment
Pregnancy & Lactation
Pregnancy: Category B
Avoid in 1st trimester; safe in 2nd and 3rd. Use vaginal preparation if possible.
Lactation: Caution
For single 2g dose: discontinue breastfeeding for 12-24 hours.
Top Drug Interactions
| Interacting Drug | Effect | Severity |
|---|---|---|
| Alcohol | DISULFIRAM-LIKE REACTION — severe nausea, flushing, vomiting | Major |
| Warfarin | Significantly increased INR | Major |
| Phenytoin | Increased phenytoin levels | Moderate |
| Lithium | Increased lithium toxicity | Major |
| Disulfiram | Acute psychosis | Major |
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Side Effects
Common
- Metallic taste
- Nausea
- Headache
- Dark urine
- Furred tongue
Serious / Discontinue If
- Peripheral neuropathy (prolonged use)
- Seizures
- Pancreatitis
- C. difficile (paradoxically)
- Aseptic meningitis
Contraindications
- Hypersensitivity
- First trimester pregnancy
- Active alcohol use
Available Indian Brands
| Brand | Manufacturer | Price (approx) |
|---|---|---|
| Flagyl 400 | Abbott | 15 tab ₹35 |
| Metrogyl 400 | JB Chemicals | 15 tab ₹28 |
| Aristogyl 400 | Aristo | 15 tab ₹25 |
Patient Counseling Points
- STRICTLY AVOID ALCOHOL during and 48 hours after
- Take with food to reduce nausea
- Urine may turn dark — harmless
- Report numbness or tingling
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References
- BNF — Metronidazole
- IDSA C. diff Guidelines 2021
- WHO Amoebiasis Treatment