Augmentin vs. Metronidazole
See how Augmentin and Metronidazole compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Augmentin covers a broad range of bacteria and is the go-to for sinus, ear, lung, skin, and urinary infections, while metronidazole targets anaerobic bacteria and certain parasites.
Metronidazole requires strict alcohol avoidance due to a disulfiram-like reaction, while Augmentin's main risks are diarrhea and, rarely, liver injury.
Metronidazole is generally more affordable than Augmentin at typical pharmacy list prices, though both are widely covered by insurance.
Augmentin vs. Metronidazole Drug Summary
Augmentin
Augmentin combines amoxicillin, a penicillin-class antibiotic, with clavulanate, which blocks the bacterial enzymes that would otherwise destroy amoxicillin. It treats a wide range of bacterial infections, including ear, sinus, lung, skin, and urinary infections. It comes as tablets, chewables, or liquid, usually taken two or three times a day with food.
Metronidazole
Metronidazole is a nitroimidazole antibiotic that targets anaerobic bacteria and certain parasites rather than the broad bacterial range Augmentin covers. It's the standard treatment for infections like bacterial vaginosis, trichomoniasis, and intra-abdominal abscesses caused by anaerobes. It's taken as an oral tablet or capsule, typically two to four times a day, and alcohol must be avoided during treatment.
Augmentin vs. Metronidazole Side Effects
Augmentin
Metronidazole
Augmentin vs. Metronidazole Dosage
Augmentin
Metronidazole
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg/125 mg q8h | At the start |
| Maximum dose | 2000 mg/125 mg q12h | If needed |
| Dose changes | 4 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 500-750 mg three times/day | If needed |
| Dose changes | 2 increases | As tolerated |
Augmentin
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg/125 mg q8h | At the start |
| Maximum dose | 2000 mg/125 mg q12h | If needed |
| Dose changes | 4 increases | As tolerated |
Metronidazole
| STAGE | DOSE | WHEN |
| Starting dose | 250 mg three times daily | Days 1-7 |
| Maximum dose | 500-750 mg three times/day | If needed |
| Dose changes | 2 increases | As tolerated |
Augmentin vs. Metronidazole Indications
Augmentin
Augmentin is FDA-approved for common bacterial infections of the ears, sinuses, lungs, urinary tract, and skin. Its added clavulanate component lets it work against bacteria that have become resistant to amoxicillin alone.
Lower respiratory tract infections
Acute bacterial otitis media
Acute bacterial sinusitis
Skin and skin structure infections
Urinary tract infections
Metronidazole
Metronidazole is FDA-approved for infections caused by anaerobic bacteria and certain parasites, including trichomoniasis, amebiasis, and bacterial vaginosis. It's also used off-label, usually combined with other drugs, for H. pylori and C. difficile infections.
Trichomoniasis
Bacterial vaginosis
Amebiasis
Intra-abdominal infections (abscess, peritonitis)
Anaerobic bacterial infections
Augmentin vs. Metronidazole Pros and Cons
Augmentin
Augmentin's added clavulanate lets it fight bacteria that produce enzymes resistant to plain amoxicillin, making it useful for a wide range of common infections. It's a well-established first-line option with pediatric-friendly forms and no FDA boxed warning.
Pros
Covers a much broader range of bacteria, including beta-lactamase producers
Available in chewable tablets and pediatric suspension formulations
No FDA boxed warning, unlike metronidazole's carcinogenicity warning
First-line option for common ear, sinus, and urinary tract infections
Cons
More likely to cause diarrhea and stomach upset than metronidazole
Unsafe for anyone with a history of penicillin allergy or amoxicillin-related liver injury
Carries a rare but serious risk of hepatotoxicity
Typically costs more, roughly $80 to $150 per month without insurance
Metronidazole
Metronidazole works differently, targeting anaerobic bacteria and parasites that Augmentin can't reach, making it the standard treatment for certain gynecologic and abdominal infections. It's an older, well-established drug, but it carries unique warnings around alcohol use and nervous system side effects.
Pros
First-line treatment for trichomoniasis and bacterial vaginosis, which Augmentin doesn't treat
Effective against anaerobic infections that don't respond to penicillin-class drugs
Roughly $15 to $40 per month without insurance, often cheaper than Augmentin
Available in oral, IV, topical, and vaginal forms
Cons
Carries an FDA boxed warning for carcinogenicity seen in animal studies
Must avoid alcohol during treatment and for several days after due to a severe reaction
Risk of neurologic side effects like seizures, peripheral neuropathy, and encephalopathy
Doesn't treat common respiratory, sinus, or ear infections that Augmentin covers
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