Amox clav, short for amoxicillin-clavulanate (brand name Augmentin), is a combination antibiotic used to treat bacterial infections that regular amoxicillin can’t handle on its own. It’s prescribed for sinus infections, ear infections, lower respiratory infections, skin infections, and urinary tract infections. The “clav” part is what makes it different from plain amoxicillin, giving it the ability to fight bacteria that have learned to resist standard antibiotics.
How Amox Clav Works
Amoxicillin is a penicillin-type antibiotic that kills bacteria by breaking apart their cell walls. The problem is that many bacteria have evolved a defense: they produce enzymes called beta-lactamases that destroy amoxicillin before it can do its job. This is where clavulanate comes in. Clavulanate acts as a decoy. It binds to those protective enzymes and permanently disables them, leaving the bacteria defenseless against the amoxicillin.
Think of it this way: amoxicillin is the weapon, and clavulanate is the shield-breaker. The combination covers a broader range of bacteria than amoxicillin alone, including staph bacteria (MSSA), certain gut bacteria, and the anaerobic bacteria found in animal and human bite wounds. Your doctor will only prescribe the combination when there’s reason to believe the infection involves these resistant bacteria. If plain amoxicillin would work, the combination isn’t recommended.
Infections It Treats
Sinus Infections
Amox clav is a first-line antibiotic for acute bacterial sinusitis. Updated 2025 guidelines from the American Academy of Otolaryngology recommend amoxicillin with or without clavulanate as the go-to treatment, typically for 5 to 7 days in most adults. If your doctor suspects the bacteria causing your sinus infection produce beta-lactamase enzymes, they’ll lean toward adding clavulanate to the prescription rather than using amoxicillin alone.
Ear Infections
Acute bacterial ear infections (otitis media) are one of the most common reasons amox clav is prescribed, especially in children. The bacteria most often responsible for stubborn ear infections are the same resistant strains that clavulanate is designed to handle. If a child has already tried plain amoxicillin without improvement, amox clav is often the next step.
Lower Respiratory Infections
This includes bacterial bronchitis and some forms of pneumonia caused by resistant bacteria. These infections tend to be more serious, and the broader coverage of the combination antibiotic helps ensure the treatment works against the specific bacteria involved.
Skin and Soft Tissue Infections
Infected wounds, cellulitis, and abscesses caused by staph, certain gut bacteria, or mixed bacterial populations can be treated with amox clav. It’s particularly useful for bite wounds, both animal and human, because the bacteria introduced through bites are often a mix of species that include anaerobes. The combination covers that broader bacterial profile in a single prescription.
Urinary Tract Infections
When a UTI is caused by resistant bacteria, amox clav can be effective. However, other antibiotics are more commonly used as first-line UTI treatments, so you’re more likely to receive amox clav for a UTI if lab results show the bacteria involved are resistant to simpler options.
Side Effects to Expect
The most common side effect is diarrhea, and it’s not rare. Pooled clinical data show that about 1 in 8 people who take amox clav will experience diarrhea, compared to roughly 1 in 18 on a placebo. The clavulanate component is largely responsible for the GI disruption. Taking the medication with food can help reduce stomach upset, though this isn’t a guarantee.
Other common side effects include nausea, vomiting, and skin rash. Allergic reactions can occur, particularly in people with a known penicillin allergy. Since amoxicillin is a penicillin, anyone who has had a serious allergic reaction to penicillin should not take amox clav.
Important Interactions
If you take a blood thinner like warfarin, amox clav can increase its effect and raise your bleeding risk. Multiple case reports have documented this interaction, so your doctor may want to monitor your blood clotting levels more closely during and shortly after your antibiotic course. Make sure your prescriber knows about all medications you’re currently taking.
Forms and Storage
Amox clav comes in tablets, chewable tablets, and a liquid suspension. The liquid form is commonly prescribed for children and for adults who have difficulty swallowing pills. Once the liquid is mixed at the pharmacy, it needs to be refrigerated and has a limited shelf life: 7 to 10 days depending on the formulation. Any leftover suspension should be thrown away after that window. Tablets can be stored at room temperature.
The medication is available in several strengths. Your doctor chooses the specific formulation based on the type and severity of the infection, your body weight (especially important for children), and kidney function. Different tablet strengths are not interchangeable on a milligram-for-milligram basis because the ratio of amoxicillin to clavulanate varies between products.
Why Your Doctor Chose It Over Plain Amoxicillin
If you’ve been prescribed amox clav instead of regular amoxicillin, it’s because your doctor suspects the bacteria causing your infection can resist amoxicillin on its own. This might be because of the type of infection (bite wounds, for example, almost always warrant the combination), because a previous round of amoxicillin didn’t work, or because local resistance patterns in your area suggest plain amoxicillin is less reliable. The clavulanate doesn’t add extra antibiotic power on its own. It simply removes the bacteria’s ability to defend against the amoxicillin that’s already there.