Amoxicillin interactions to avoid

Amoxicillin interacts with anticoagulants, antigout medications, antibacterials, and birth control pills

By Keith Gardner, R.Ph. | Oct. 30, 2023

Amoxicillin is a prescription-only, broad-spectrum antibiotic originally derived from penicillin that is approved by the U.S. Food and Drug Administration (FDA) to treat a wide range of respiratory bacterial infections, such as pneumonia and bronchitis, as well as infections of the ear, nose, throat, urinary tract infections, and skin. It can also be used together with other medicines, such as the proton pump inhibitor lansoprazole, to treat stomach ulcers (H. pylori stomach infections). It kills bacteria by blocking their ability to make and repair their protective cell walls. Like all antibiotics, amoxicillin is not effective against viral infections.

Amoxicillin is generic for the brand-name products Amoxil, Trimox, and Larotid. Amoxicillin is also available combined with clavulanate, which enhances the antibacterial effect, as the generic or as brand-name Augmentin. Dosage forms available include amoxicillin capsules, chewable tablets, and pediatric oral suspensions. For most infections, amoxicillin is prescribed to be taken three times daily for 10 to 14 days. Those taking amoxicillin may experience side effects, but drug interactions taken for existing medical conditions are also possible. It is important to be aware of how amoxicillin may affect the action of other drugs and, conversely, how other drugs (and foods) may affect amoxicillin.

Key takeaways:

Amoxicillin interacts with oral anticoagulants, such as warfarin, leading to a risk of bleeding. Adjustments in the dose of the oral anticoagulant may be necessary to maintain the desired blood levels.
Blood level concentrations of amoxicillin can be higher if taken with probenecid, a gout prevention pill, which could lead to increased side effects. Taking amoxicillin with probenecid is not recommended.
Taking allopurinol, another gout-prevention medicine, and amoxicillin together may increase the incidence of skin rashes or hives.
Certain antibacterials, such as chloramphenicol, erythromycin, sulfamethoxazole, and tetracycline, may interfere with the efficacy of amoxicillin and should not be taken at the same time.
There has been concern in the past about whether taking antibiotics can interfere with the effectiveness of birth control pills and lead to unexpected pregnancy. The overall risk is small and applies more to some specific antibacterials, notably rifampin in the rifamycin class of drugs, than with amoxicillin.
Amoxicillin can be taken without regard to meals, as the presence or absence of food does not alter its effectiveness.
When prescribed amoxicillin while taking any other medicine that may interact with it, discuss this concern with a healthcare provider.

Amoxicillin drug interactions

Most potential interactions with amoxicillin are considered mild or moderate and not dangerous, as is true of other penicillin antibiotics. There are certain prescription drugs that should be avoided when taking amoxicillin. This includes some gout medications, blood thinners (anticoagulants), oral birth control pills, and certain types of antibacterials. None of these interactions mean that they cannot be used with amoxicillin, but they do call for awareness and monitoring.

Blood thinners

Amoxicillin may make it harder for the body to absorb anticoagulants (blood thinners) like warfarin (brand name Coumadin). Anticoagulants are prescribed to help prevent blood clots from forming, typically for patients at risk of clotting following surgery. Taking amoxicillin concurrently may amplify the drugs’ anticoagulant effects and even lead to dangerous conditions like warfarin toxicity or internal bleeding. However, most people who take amoxicillin short-term (10 to 14 days) while taking an anticoagulant do not experience these issues. Your healthcare professional should monitor you for symptoms of possible serious side effects.

Gout medications

Probenecid, also known by the brand name Probalan, is a medication used to treat gout. It works by raising the amount of uric acid released through the urine. This lowers uric acid levels in the blood. Taking probenecid with amoxicillin may increase the levels of amoxicillin in the blood because it makes it more difficult for the kidneys to filter antibiotics from the body. This, in turn, may increase the risk of side effects.

Allopurinol, a common generic gout medication also known by the brand name Zyloprim, may make a person more sensitive to amoxicillin when the two drugs are taken together. This may lead to a greater chance of developing an allergic reaction to amoxicillin, particularly a skin rash.

Antibacterials

Certain antibacterials, such as chloramphenicol, macrolides (e.g., erythromycin, clarithromycin, azithromycin), sulfonamides (e.g., Bactrim), and tetracyclines (e.g., Sumycin, doxycycline), may interfere with and reduce the bactericidal effects of amoxicillin. Always consult a healthcare professional before combining amoxicillin with other antibiotics or antibacterial medicines.

Birth control pills

In the past, it was thought that taking antibiotics with hormonal birth control pills or patches might make them less effective, increasing the risk of pregnancy. It has since been determined that only antibacterials that speed up the metabolism of hormonal contraceptives, such as rifampin (brand names Rifadin and Rimactane) in the rifamycin class, can potentially interact and reduce their effectiveness. According to a 2017 database review, no evidence of drug interactions between hormonal contraception and non-rifamycin antibiotics was found.

Amoxicillin food interactions

According to the amoxicillin product labeling, there are no drug-food interactions of concern. Taking amoxicillin with or without food has minimal effects on the absorption of amoxicillin into the bloodstream, therefore, it can be taken without regard to meals. Amoxicillin combined with clavulanate may cause some gastrointestinal (GI) discomfort, so it is recommended to be taken before meals to minimize possible GI side effects.

Other amoxicillin interactions

The following interactions with amoxicillin are not as consequential as the previously mentioned drug-drug interactions. Any concerns or questions one may have about specific foods, over-the-counter (OTC) medications, or vitamins or herbal supplements should be discussed with a healthcare professional.

Amoxicillin and alcohol

Although drinking alcohol while taking amoxicillin is not prohibited, most healthcare professionals recommend avoiding alcohol because it may increase common amoxicillin side effects such as nausea and abdominal discomfort. Alcohol may also weaken the immune system and lead to dehydration which may make the infection more difficult to treat.

Amoxicillin and oral live vaccines

Antibacterial drugs such as amoxicillin can impact the effectiveness of the oral typhoid and cholera vaccines. It is recommended to delay vaccination with oral typhoid vaccine by more than three days (72 hours) and delay oral cholera vaccine by more than 14 days following a course of therapy of amoxicillin.

Amoxicillin and bromelain

Certain antibiotics, including amoxicillin, may interact with bromelain, an enzyme extract derived from pineapples. Taking bromelain might increase how much amoxicillin is absorbed, which may increase the effects, and side effects, such as stomach pain, of the drug.

Amoxicillin and guar gum

Guar gum, fiber from the seed of the guar plant, is used to treat diarrhea, irritable bowel syndrome (IBS), constipation, high blood pressure, and high cholesterol. Guar gum may reduce the absorption of amoxicillin, and it is recommended it be taken two hours before or two hours after taking the amoxicillin.

How to minimize amoxicillin interactions

While many medications can be taken at the same time as amoxicillin safely, there are several medications that can have potentially serious negative outcomes when taken with amoxicillin. To avoid potential problems before starting a new prescription, it’s always best to give the prescribing healthcare provider a list of all prescription and over-the-counter medications, vitamins, herbs, and supplements being taken, as well as any existing medical conditions. By sharing this information, it is much easier to prevent any interactions before they occur. It may result in a different antibiotic, such as the cephalosporin antibiotics cefaclor or cephalexin, or a macrolide, such as clarithromycin, being prescribed.

When to talk to a healthcare provider about amoxicillin interactions

Severe drug interactions are rare when taking amoxicillin. Overall, the drug is very safe. Tell your healthcare provider about any adverse effects experienced, even if they may not be related to amoxicillin. This article doesn’t provide a complete list of all of the potential interactions, so it’s important to be conscious of any untoward effects from taking amoxicillin with another drug and to seek medical advice if any occur.

Contact the prescribing healthcare provider immediately if any of the following symptoms occur while taking amoxicillin with another drug: