Amoxicillin-clavulanate (commonly sold as Augmentin) has several notable interactions with other medications that can either raise your risk of side effects or reduce how well the antibiotic works. The most important ones involve blood thinners, gout medications, methotrexate, and certain live vaccines.
Warfarin and Other Blood Thinners
If you take warfarin, amoxicillin-clavulanate can push your blood-clotting levels higher than expected, increasing the risk of serious bleeding. This happens even though the antibiotic doesn’t directly interfere with the liver enzymes that break down warfarin. The likely mechanism involves changes to gut bacteria that affect vitamin K absorption, which your body needs to regulate clotting.
This doesn’t necessarily mean you can’t take both, but your clotting levels (measured by a blood test called INR) will need closer monitoring during and shortly after your antibiotic course. If you’re on warfarin and get prescribed amox-clav, make sure the prescribing doctor knows about your blood thinner so they can arrange extra blood checks.
Allopurinol and Skin Rash Risk
Allopurinol, a medication commonly used for gout, roughly triples your chance of developing a skin rash while on amoxicillin-clavulanate. In one study, 22% of patients taking both drugs together developed a rash, compared to about 6% of those on amoxicillin alone. A larger follow-up study confirmed the pattern: 13.9% rash incidence with allopurinol versus 5.7% without it.
The rash is typically not dangerous, but it can be uncomfortable and sometimes makes it hard to tell whether you’re having a true allergic reaction to the antibiotic. If you take allopurinol daily, let your prescriber know before starting amox-clav so they can weigh the options.
Methotrexate
Methotrexate is used at low doses for conditions like rheumatoid arthritis and psoriasis. Amoxicillin-clavulanate slows the kidneys’ ability to clear methotrexate from your body, causing it to build up in your bloodstream. Even at low doses, elevated methotrexate levels can damage the liver, suppress bone marrow (which makes blood cells), and harm the kidneys, lungs, or gut lining.
In one reported case, a patient developed abnormal liver function tests after just four doses of amoxicillin-clavulanate while on methotrexate. If you take methotrexate regularly, your doctor may choose a different antibiotic or monitor your blood work more closely during treatment.
Probenecid
Probenecid, another gout medication, blocks the kidney transporters that normally flush amoxicillin out of your body. This reduces amoxicillin clearance by 50 to 70%, meaning the antibiotic stays in your blood at much higher concentrations for longer. While doctors sometimes use this interaction intentionally to boost antibiotic levels, taking probenecid without your prescriber’s awareness could lead to unexpectedly high drug exposure and a greater chance of side effects like diarrhea or nausea.
Oral Typhoid and Cholera Vaccines
Amoxicillin-clavulanate can kill the live bacteria in oral typhoid and oral cholera vaccines before your immune system has a chance to respond. The CDC recommends waiting at least 72 hours after finishing your antibiotic course before getting the oral typhoid vaccine, and at least 14 days before the oral cholera vaccine. Injectable typhoid vaccine is not affected, so if your travel timeline is tight, that’s an alternative worth discussing.
Alcohol
There is no direct chemical interaction between alcohol and amoxicillin-clavulanate. It won’t cause the severe flushing and vomiting reaction that some other antibiotics (like metronidazole) are known for. That said, amox-clav already tends to cause nausea and diarrhea on its own, and alcohol can make those symptoms worse. Drinking can also impair sleep and immune function while your body is fighting an infection, so most people find it easier to skip alcohol until the course is done.
Timing With Probiotics
Probiotics aren’t dangerous to combine with amox-clav, but taking them at the same time defeats the purpose. The antibiotic will kill probiotic bacteria before they can do anything useful. If you want to use a probiotic to help with antibiotic-related digestive issues, wait at least two hours after your amox-clav dose before taking it. You can start the probiotic on the same day you begin antibiotics.
Why You Should Take It With Food
This isn’t a substance to avoid, but it’s closely related to what readers searching this topic need to know. Amoxicillin-clavulanate absorbs best when taken at the start of a meal. In clinical testing, taking it on an empty stomach reduced amoxicillin absorption by about 25% compared to taking it with food. Meanwhile, the clavulanate component absorbs well on an empty stomach or at the start of a meal but drops significantly if you take the tablet 30 minutes after a high-fat meal.
The sweet spot is simple: take your dose right as you begin eating. This maximizes absorption of both components and also helps reduce the nausea and stomach upset that amox-clav is notorious for.