Amoxicillin has been prescribed more than any other oral antibiotic in the United States for over 25 years, and the combination form Augmentin (amoxicillin-clavulanate) sits not far behind. If you have been handed a prescription labeled amoxicillin and clavulanate potassium used for some infection, the clavulanate component is there to block bacterial resistance enzymes that would otherwise inactivate plain amoxicillin. For more on infection treatment, see our medical conditions guide.
How Plain Amoxicillin Works
Amoxicillin is a penicillin-class antibiotic. It binds to proteins in bacterial cell walls, preventing the wall from forming properly, which kills the bacteria. It is effective against many aerobic gram-positive and some gram-negative organisms.
The FDA prescribing information for amoxicillin lists approvals for ear, nose, throat, skin, urinary tract, and lower respiratory infections, plus H. pylori eradication and Lyme disease.
What Clavulanate Adds to the Mix
Some bacteria produce beta-lactamase, an enzyme that breaks down amoxicillin before it can work. Clavulanate potassium is a beta-lactamase inhibitor. It binds and deactivates the enzyme, letting amoxicillin do its job. Augmentin (amoxicillin-clavulanate) is therefore effective against bacteria that resist plain amoxicillin.
Common amoxicillin-clavulanate uses include acute bacterial sinusitis, otitis media with resistance, community-acquired pneumonia, skin and soft tissue infections from animal bites, complicated UTIs, and intra-abdominal infections. The FDA label for Augmentin lists these indications.
Standard Adult Dosing
Plain amoxicillin is typically dosed at 500 mg every 8 hours or 875 mg every 12 hours. Augmentin comes in multiple strengths expressed as amoxicillin/clavulanate in milligrams: 500/125 every 8 hours, 875/125 every 12 hours, or 1000/62.5 (XR) every 12 hours for severe infections.
Mayo Clinic notes that courses are usually 7 to 14 days, with shorter protocols acceptable for uncomplicated sinusitis or UTI. Pediatric Augmentin is dosed by weight.
Common Infections Where Augmentin Is First Line
For adults with acute bacterial sinusitis, the Infectious Diseases Society of America recommends amoxicillin-clavulanate as first-line treatment because of rising resistance in Streptococcus pneumoniae and Haemophilus influenzae. Animal and human bite wounds are another classic Augmentin indication because oral flora include beta-lactamase producers.
Aspiration pneumonia, diabetic foot infections, and complicated pelvic infections also benefit from the extra coverage clavulanate provides.
When Plain Amoxicillin Is Enough
Strep throat, dental infections, uncomplicated ear infections in children, and H. pylori triple therapy can usually be treated with plain amoxicillin because the target bacteria do not commonly produce beta-lactamase. Using Augmentin unnecessarily increases side effects (especially diarrhea) and drives resistance.
Your prescriber chooses between the two based on the likely pathogen, your history, and local resistance patterns. Our conditions guide has more on antibiotic stewardship.
Side Effects and Safety Profile
Amoxicillin-clavulanate causes diarrhea in roughly 15 percent of users, about twice the rate of plain amoxicillin, because clavulanate disrupts gut flora. Other side effects include nausea, vomiting, yeast infections, and rash. Clostridioides difficile colitis is a serious complication that can occur during or after treatment.
Allergic reactions to any penicillin-class drug range from mild rash to anaphylaxis. The CDC notes that most reported penicillin allergies are not true IgE-mediated reactions and can often be re-evaluated by an allergist.
When to seek emergency care: Call 911 or go to the ER immediately if you experience difficulty breathing, swelling of the face, lips, or throat, severe rash with fever, widespread hives, or severe watery or bloody diarrhea after taking amoxicillin or Augmentin.
Who Should Not Take Augmentin
People with a history of severe penicillin allergy should avoid any amoxicillin product. Augmentin is contraindicated in patients with a prior history of amoxicillin-clavulanate-associated cholestatic jaundice or hepatic dysfunction, a rare but serious reaction that typically appears within six weeks of treatment.
Kidney impairment requires dose adjustment. Pregnant patients may use Augmentin if clearly needed, with shared decision-making between patient and prescriber.
Frequently Asked Questions
What is amoxicillin-clavulanate most commonly used for?
Acute bacterial sinusitis, ear infections that have not responded to plain amoxicillin, animal and human bite wounds, and certain skin infections are the most common uses. It is also used for some respiratory and urinary tract infections.
Is Augmentin stronger than amoxicillin?
Not exactly. Augmentin covers more bacterial strains because clavulanate blocks beta-lactamase enzymes. For bacteria that are already susceptible to plain amoxicillin, plain amoxicillin works just as well with fewer side effects.
Can amoxicillin-clavulanate treat a UTI?
Yes, but it is not first-line for uncomplicated UTIs. Trimethoprim-sulfamethoxazole, nitrofurantoin, and fosfomycin are typically preferred. Augmentin is used when cultures show resistance to those drugs.
Why does Augmentin cause more diarrhea than amoxicillin?
The clavulanate component disrupts gut flora more than amoxicillin alone does. Taking Augmentin with food helps reduce nausea and diarrhea, and probiotic use during treatment may lower risk though evidence is mixed.
The Bottom Line
Amoxicillin treats ear, nose, throat, skin, urinary, and lower respiratory infections, while amoxicillin-clavulanate (Augmentin) adds coverage for beta-lactamase-producing bacteria. Plain amoxicillin is preferred when the expected bacteria are susceptible. Finish the full course as directed, take it with food, and report severe diarrhea, rash, or breathing problems to your prescriber immediately.