Home › Compound Library › Metronidazole (Flagyl)

Metronidazole (Flagyl)

Antibioticprescriptionoral · inferred

Nitroimidazole antibiotic/antiprotozoal targeting anaerobic bacteria and parasites. Reduced intracellularly to cytotoxic intermediates that damage DNA. First-line for C. difficile, bacterial vaginosis, trichomoniasis, anaerobic infections, and H. pylori (triple therapy). Active hydroxy metabolite has ~50% of parent antimicrobial activity. Disulfiram-like reaction with alcohol. Crosses blood-brain barrier well.

Projected serum levels — 500 mg, once daily

Metronidazole (Flagyl)
Metronidazole (Flagyl) modeled serum levels, 500 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 125 250 375 500 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 500 mg once daily (oral).

Modeled steady state after ~1 days: peak ≈ 357 mg, trough ≈ 5.9 mg body load. Population-based estimate over 15 days for a 500 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Antibiotic
Route modeled
Oral
Model confidence
inferred
Half-life
8 h
Common dose
500 mg
Suggested maximum
2k mg/day
Reference dose range
250–2k mg (single dose)
Suggested cadence
once daily
Validated against
500 mg oral — Cmax 12 mg/L at 1.5 h

Documented interactions

  • danger
    Candesartan + Metronidazole (Flagyl) CYP inhibition

    Metronidazole (Flagyl) reversible_inhibitor of CYP2C9 predicted to change Candesartan AUC by ~3.33x

  • danger
    Celecoxib (Celebrex) + Metronidazole (Flagyl) CYP inhibition

    Metronidazole (Flagyl) reversible_inhibitor of CYP2C9 predicted to change Celecoxib (Celebrex) AUC by ~2.97x

  • danger
    Efavirenz (Sustiva) + Metronidazole (Flagyl) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Metronidazole (Flagyl) AUC by ~0.42x

  • danger
    Glipizide (Glucotrol) + Metronidazole (Flagyl) CYP inhibition

    Metronidazole (Flagyl) reversible_inhibitor of CYP2C9 predicted to change Glipizide (Glucotrol) AUC by ~2.47x

  • danger
    Meloxicam (Mobic) + Metronidazole (Flagyl) CYP inhibition

    Metronidazole (Flagyl) reversible_inhibitor of CYP2C9 predicted to change Meloxicam (Mobic) AUC by ~2.20x

  • danger
    Phenytoin (Dilantin) + Metronidazole (Flagyl) CYP inhibition

    Metronidazole (Flagyl) reversible_inhibitor of CYP2C9 predicted to change Phenytoin (Dilantin) AUC by ~2.20x

Serum checks 87 modeled interaction pairings for metronidazole (flagyl) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Pharmacokinetics of metronidazole and its principal metabolites Lamp KC et al. · Clinical Pharmacokinetics, 1999 DOI

    Definitive PK review establishing metronidazole half-life of 6-10 hours, near-complete oral absorption, active hydroxy metabolite with 12-hour half-life and 30-65% of parent activity, and hepatic oxidative metabolism.

  2. Vancomycin versus metronidazole for the treatment of Clostridium difficile infection: a systematic review and meta-analysis Di X et al. · International Journal of Antimicrobial Agents, 2015 DOI

    Meta-analysis of 8 RCTs finding metronidazole effective for mild-to-moderate C. difficile infection but inferior to oral vancomycin for severe cases, informing current IDSA treatment guidelines.

2 published studies referenced in the app, each with a plain-language summary.