Amoxicillin vs. Flagyl
See how Amoxicillin and Flagyl compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Amoxicillin, a penicillin-class antibiotic, treats bacterial infections like ear, throat, and urinary tract infections, while Flagyl targets anaerobic bacteria and parasites such as trichomoniasis.
Both drugs are taken by mouth multiple times a day, but Flagyl requires strict alcohol avoidance due to a severe reaction risk that amoxicillin does not carry.
Amoxicillin is generally cheaper and better tolerated, while Flagyl carries a boxed warning for carcinogenicity shown in animal studies.
Amoxicillin vs. Flagyl Drug Summary
Amoxicillin
Amoxicillin is an aminopenicillin antibiotic used to treat common bacterial infections of the ear, nose, throat, lungs, skin, and urinary tract. It also plays a role in combination therapy for H. pylori eradication. It comes as a capsule, tablet, chewable tablet, or liquid, usually taken two to three times a day.
Flagyl
Flagyl (metronidazole) is a nitroimidazole antimicrobial used to treat trichomoniasis, amebiasis, and infections caused by anaerobic bacteria. It is also used off-label, in a specific regimen, for bacterial vaginosis. It comes as an oral tablet taken multiple times a day, with treatment length depending on the infection.
Amoxicillin vs. Flagyl Side Effects
Amoxicillin
Flagyl
Amoxicillin vs. Flagyl Dosage
Amoxicillin
Flagyl
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg every 8 hours | At the start |
| Maximum dose | 1 g three times daily | If needed |
| Dose changes | 4 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 7.5 mg/kg every 6 hours | Days 1-7 |
| Dose changes | 3 increases | As tolerated |
Amoxicillin
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg every 8 hours | At the start |
| Maximum dose | 1 g three times daily | If needed |
| Dose changes | 4 increases | As tolerated |
Flagyl
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 7.5 mg/kg every 6 hours | Days 1-7 |
| Dose changes | 3 increases | As tolerated |
Amoxicillin vs. Flagyl Indications
Amoxicillin
Amoxicillin is FDA-approved for a wide range of common bacterial infections, including those affecting the ears, sinuses, throat, lungs, skin, and urinary tract. It is also used, together with other drugs, to eradicate H. pylori bacteria linked to stomach ulcers. It is not effective against viral infections like colds or the flu.
Ear, nose, and throat infections
Lower respiratory tract infections
Skin and skin structure infections
Urinary tract infections
Flagyl
Flagyl (metronidazole) is FDA-approved to treat trichomoniasis, amebiasis, and infections caused by anaerobic bacteria. It is also commonly used off-label, in a specific dosing regimen, for bacterial vaginosis. It is not effective against viral infections.
Trichomoniasis (symptomatic and asymptomatic)
Amebiasis
Anaerobic bacterial infections
Bacterial vaginosis (off-label use)
Amoxicillin vs. Flagyl Pros and Cons
Amoxicillin
Amoxicillin has a long safety record, broad pediatric use, and is one of the most affordable generic antibiotics available. It does not carry the alcohol restrictions or carcinogenicity warning found with Flagyl, but it will not treat anaerobic bacterial or protozoal infections.
Pros
Well-tolerated with a long safety record
Available as a low-cost generic, roughly $11 to $25 a month
Safe to take alongside alcohol
Cons
Not effective against anaerobic bacteria or parasites
Can cause allergic reactions in penicillin-sensitive patients
Overuse has contributed to rising bacterial resistance
Flagyl
Flagyl covers anaerobic bacterial and protozoal infections that amoxicillin cannot treat, including trichomoniasis and amebiasis. Its list price varies widely by formulation, and it carries a boxed warning along with a strict alcohol restriction that amoxicillin does not have.
Pros
Effective against anaerobic bacteria and parasites amoxicillin misses
Single 2 g dose available for trichomoniasis
Long history of clinical use dating back to 1963
Cons
Boxed warning for carcinogenicity seen in animal studies
Must avoid alcohol during and after treatment due to a severe reaction risk
Metallic taste is a common complaint
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