Metronidazole vs. Flagyl

See how Metronidazole and Flagyl compare on approved uses, dosing, side effects, and cost.

Key Takeaways

  • Metronidazole and Flagyl contain the exact same active ingredient, so their effects, risks, and drug interactions are identical.

  • Flagyl brand-name tablets have been discontinued in the US, so generic metronidazole is now the only way to get this medication as a tablet.

  • Both carry the same boxed warning about carcinogenicity in animal studies and the same contraindications with alcohol and disulfiram.

Metronidazole vs. Flagyl Drug Summary

Metronidazole

Metronidazole is a nitroimidazole antibiotic used to treat trichomoniasis, amebiasis, bacterial vaginosis, and serious anaerobic bacterial infections. It comes as an oral tablet or capsule, with IV, topical, and vaginal forms available depending on the infection being treated.

Flagyl

Flagyl is the original brand name for metronidazole, a nitroimidazole antibiotic used to treat trichomoniasis, amebiasis, and anaerobic bacterial infections. The brand-name tablet has been discontinued, so Flagyl now refers mainly to the generic oral and IV metronidazole that replaced it.

Metronidazole vs. Flagyl Side Effects

Metronidazole

Most common
nausea (up to 12%)
headache (up to 6%)
diarrhea (up to 5%)
metallic taste (up to 4%)

Flagyl

Most common
nausea (up to 12%)
headache (up to 6%)
diarrhea (up to 5%)
metallic taste (up to 4%)

Metronidazole vs. Flagyl Dosage

Metronidazole

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 250 mg 3x daily Days 1-7
Maximum dose 500-750 mg 3x daily If needed
Dose changes 2 increases As tolerated

Flagyl

Dosage
Dosage Table
STAGE DOSE WHEN
Starting dose 250 mg 3x daily Days 1-7
Maximum dose 7.5 mg/kg every 6 hrs Days 1-7
Dose changes 3 increases As tolerated

Metronidazole vs. Flagyl Indications

Metronidazole

Metronidazole is FDA-approved for a wide range of infections, including trichomoniasis, amebiasis, bacterial vaginosis, and serious intra-abdominal infections like peritonitis and abscesses. It's also used off-label for H. pylori eradication and C. diff infections.

  • Trichomoniasis (symptomatic and asymptomatic)

  • Amebiasis

  • Bacterial vaginosis

  • Intra-abdominal infections (peritonitis, abscess)

  • Rosacea (topical form)

Flagyl

Flagyl was originally approved for trichomoniasis, amebiasis, and anaerobic bacterial infections, including treatment of the partners of people diagnosed with trichomoniasis. It's sometimes used off-label for bacterial vaginosis, though that regimen wasn't part of its original approval.

  • Trichomoniasis (symptomatic and asymptomatic)

  • Treatment of partners of trichomoniasis patients

  • Amebiasis

  • Anaerobic bacterial infections

  • Bacterial vaginosis (off-label)

Metronidazole vs. Flagyl Pros and Cons

Metronidazole

Because metronidazole is the generic form, it comes in more formulations and is FDA-approved for a broader set of infections than the original Flagyl label covered. It remains one of the most affordable and widely stocked generic antibiotics.

Pros

  • Available as oral, IV, topical gel, and vaginal gel

  • FDA-approved for bacterial vaginosis and rosacea

  • Approved for intra-abdominal infections like peritonitis

Cons

  • Generic tablets can look different between refills or pharmacies

  • No brand-name version is currently marketed in the US

  • Multiple formulations can make dosing selection more complex

Flagyl

Flagyl was the original brand for metronidazole, but the manufacturer discontinued brand-name tablets, so prescriptions now rely on generic versions. Its original approval was narrower than current generic labeling, excluding bacterial vaginosis and rosacea.

Pros

  • Includes an FDA-approved weight-based IV regimen for anaerobic infections

  • Original label covers treating asymptomatic partners of trichomoniasis patients

  • Extended-release tablet formulation available under this drug name

Cons

  • Brand-name Flagyl tablets are discontinued and unavailable

  • Original FDA approval doesn't include bacterial vaginosis or rosacea

  • Narrower set of FDA-approved indications than current generic labeling

Common Symptoms and Related Diseases You Can Explore

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