Metronidazole: Uses, Side Effects, and How to Take It
Metronidazole is an antibiotic used to treat certain bacterial infections and infections caused by protozoal parasites. It is commonly prescribed for conditions affecting the intestines, skin, mouth, pelvis, and reproductive tract, but it does not treat viral illnesses such as colds or flu.
Take metronidazole exactly as prescribed and complete the full course, even if you start feeling better. Avoid alcohol during treatment and for at least 3 days afterward, and ask a doctor or pharmacist about your specific medicines and health conditions.
Key facts at a glance
- ATC
- J01XD01
- Generic
- Metronidazole
- Class
- antibiotic-other
- Brands
- Flagyl
- Availability
- rx
- Pregnancy
- B
- Lactation
- caution
- Half-life (h)
- 8
- Onset (min)
- 60
- Duration (h)
- 8
- Routes
- oral, iv, topical, vaginal
- Forms
- tablet, capsule, cream, gel, injection
- Regions
- CN, US, EU, JP
- Monitoring
- neurological, alcohol-interaction
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 7.5mg/kg every 6 hours
- Maximum
- consult physician
- Frequency
- every 6 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
9 groupspregnancy
first trimesteruse lowest effective dose
avoid during first trimester if possible, only use if benefits clearly outweigh risks
regular prenatal monitoring
Use with caution and monitor for adverse effects.
pregnancy
second and third trimesterstandard dosing
considered safe for treating infections during second and third trimesters
standard prenatal care
lactation
breastfeedingpump and discard milk during treatment and 24 hours after
metronidazole passes into breast milk, nursing mothers should pump and discard milk during treatment and for 24 hours after completing therapy
monitor infant for gastrointestinal disturbances
Use with caution and monitor for adverse effects.
pediatric_age
infants under 8 weeksavoid if possible, use with extreme caution
not recommended in infants under 8 weeks due to immature metabolic pathways
close clinical monitoring
Use with caution and monitor for adverse effects.
pediatric_age
children 8 weeks and olderweight-based dosing
dosing based on weight, typically 15-30 mg/kg/day divided into doses
standard pediatric monitoring
geriatric
elderlyno specific adjustment needed, monitor renal function
use standard dosing but assess renal and hepatic function; increased sensitivity to side effects
monitor renal and hepatic function, watch for neurological side effects
Use with caution and monitor for adverse effects.
renal_impairment
severe renal impairmentreduce dose in severe impairment (CrCl < 10 mL/min), extend dosing interval
reduce dose by 50% or extend interval to every 12-24 hours in severe renal impairment
monitor renal function, drug levels if available
Use with caution and monitor for adverse effects.
hepatic_impairment
severe hepatic impairmentdose reduction required, reduce dose by 50%
reduce dose by 50% in severe hepatic impairment due to reduced metabolism
monitor for signs of toxicity, consider therapeutic drug monitoring
Use with caution and monitor for adverse effects.
alcohol_users
concurrent alcohol useabsolutely avoid
DO NOT consume alcohol during treatment and for 3 days after completing therapy; causes disulfiram-like reaction
educate patient on alcohol avoidance
Use of this medication in this population requires careful consideration of risks and benefits.
Statistics and clinical data
Drug class
Antimicrobial class classification
FDA approval year
Initial FDA approval date for Metronidazole
Primary indications
Primary therapeutic indications
Mechanism of action
Molecular mechanism of antimicrobial action
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 22, 2026. · Read our editorial policy