What Should You Not Take With Amoxicillin? A Guide to Safe Combinations

October 11, 2025 •

4 min read

According to a 2017 database review, a common misconception that hormonal birth control is rendered ineffective by non-rifamycin antibiotics like amoxicillin has been largely disproven. While this may be reassuring, it remains crucial to know what should you not take with amoxicillin to prevent other potentially serious drug interactions or reduced efficacy. This guide addresses common combinations and interactions to be aware of during your course of treatment.

Quick Summary

This guide explains important drug interactions to avoid while taking amoxicillin, including with blood thinners like warfarin, gout medications such as allopurinol and probenecid, and the chemotherapy drug methotrexate.

Key Points

Blood Thinners: Amoxicillin increases the risk of bleeding when taken with blood thinners like warfarin, requiring careful monitoring by a doctor.
Gout Medications: Combining amoxicillin with allopurinol significantly raises the risk of skin rash, while probenecid can increase amoxicillin levels in the body.
Methotrexate: Amoxicillin can increase the concentration of methotrexate in the bloodstream, heightening the risk of toxicity.
Certain Antibiotics: Taking amoxicillin with bacteriostatic antibiotics like tetracyclines can interfere with its bactericidal action and reduce its effectiveness.
Live Vaccines: The effectiveness of oral live vaccines for typhoid and cholera can be compromised by amoxicillin, so timing must be managed by a healthcare provider.
Alcohol and Supplements: It is generally recommended to avoid alcohol due to potential side effect worsening, and certain herbal supplements like bromelain and guar gum can alter amoxicillin absorption.
Dairy is Safe: A common myth holds that dairy interferes with amoxicillin, but studies show it does not affect absorption and is safe to consume.

Amoxicillin is a common penicillin-class antibiotic prescribed to treat a wide array of bacterial infections, such as those affecting the ears, nose, throat, and skin. While generally considered safe and effective, certain substances can interact with it, leading to adverse effects or altering its efficacy. Being aware of these interactions is a critical step toward ensuring a safe and successful recovery from your infection.

Serious Drug Interactions to Avoid with Amoxicillin

Blood Thinners (Anticoagulants)

Taking amoxicillin with certain blood thinners, particularly warfarin, can significantly increase the risk of bleeding. The mechanism behind this interaction involves the gut microbiota. Amoxicillin can alter the gut flora responsible for producing vitamin K, a vital component in the body's blood clotting process. Since blood thinners also interfere with clotting factors, combining them amplifies the risk of excessive bleeding or bruising. Your healthcare provider may recommend more frequent monitoring of your International Normalized Ratio (INR) and may adjust your warfarin dosage during and after your amoxicillin treatment. Other anticoagulants, including apixaban and rivaroxaban, also require caution.

Gout Medications

Two common gout medications have notable interactions with amoxicillin:

Allopurinol (Zyloprim): The co-administration of amoxicillin with allopurinol increases the risk of developing a skin rash. While the exact reason for this heightened risk is unknown, it's a well-documented interaction. In rare cases, this combination can trigger a severe allergic reaction known as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome. Patients taking both medications should be monitored closely for any signs of skin sensitivity, fever, or swelling.
Probenecid (Probalan): This medication, which helps lower uric acid levels, can reduce the rate at which the kidneys excrete amoxicillin. As a result, the concentration of amoxicillin in the bloodstream can become elevated, increasing the likelihood of experiencing common side effects like nausea and vomiting. For this reason, some healthcare providers advise against using this combination if possible.

Methotrexate (Trexall)

For patients undergoing treatment with methotrexate for conditions like cancer, arthritis, or psoriasis, combining it with amoxicillin requires careful management. Amoxicillin competes with methotrexate for the same clearance pathway in the kidneys, leading to higher levels of methotrexate in the body. This can increase the risk of methotrexate-related side effects, such as bleeding, skin rashes, and diarrhea. Your doctor will likely monitor your blood levels more frequently and may adjust your methotrexate dose to prevent toxicity.

Certain Other Antibiotics

While it is unusual to be prescribed two different types of antibiotics at the same time, certain classes can interfere with amoxicillin's mechanism of action. Antibiotics like tetracyclines, macrolides (e.g., erythromycin), and chloramphenicol can potentially reduce the effectiveness of amoxicillin. These are often described as bacteriostatic antibiotics, meaning they stop bacteria from growing, which can conflict with amoxicillin's bactericidal (bacteria-killing) action. Therefore, healthcare professionals typically avoid prescribing these antibiotics together.

Interactions with Supplements and Lifestyle Factors

Herbal Supplements

Bromelain: This enzyme, derived from pineapple, can increase the absorption of amoxicillin, potentially leading to higher drug levels and side effects. If you take a bromelain supplement, discuss this with your doctor.
Guar Gum: As a fiber supplement used for digestive health, guar gum can reduce the absorption of amoxicillin. It is recommended to separate the intake of guar gum from your antibiotic dose by at least two hours.

Live Vaccines

Oral live vaccines, such as those for typhoid and cholera, can have their effectiveness reduced if taken concurrently with amoxicillin. The antibiotic can kill the weakened bacteria in the vaccine, preventing your body from building the necessary immunity. Your doctor will advise you to schedule your vaccinations at a different time from your course of amoxicillin.

Alcohol

While there is no direct chemical interaction between alcohol and amoxicillin, health professionals advise against drinking during antibiotic treatment. This is because alcohol can exacerbate common amoxicillin side effects like nausea, vomiting, and diarrhea. Furthermore, alcohol can weaken your immune system, making it harder for your body to fight the underlying infection.

Comparison Table: Amoxicillin Interactions at a Glance


Substance	Interaction Type	Potential Outcome	Management
Warfarin (Blood Thinner)	Increased bleeding risk	Excessive bleeding, unusual bruising	Frequent INR monitoring, possible warfarin dose adjustment
Allopurinol (Gout)	Increased skin rash risk	Skin rashes, rare severe allergic reaction (DRESS)	Close monitoring, consider alternative antibiotic
Probenecid (Gout)	Increased amoxicillin levels	Elevated amoxicillin side effects (nausea, vomiting)	Increased monitoring, alternative antibiotic may be preferred
Methotrexate (Chemotherapy)	Elevated methotrexate levels	Increased methotrexate side effects (toxicity)	Increased monitoring, potential dose adjustment
Tetracyclines/Macrolides (Other Antibiotics)	Reduced amoxicillin effectiveness	Antibiotic treatment may fail	Avoid concurrent use, alternative prescription
Oral Live Vaccines (Typhoid/Cholera)	Reduced vaccine effectiveness	Failed immunity building	Separate vaccine and antibiotic dosing

Conclusion

While amoxicillin is a highly effective antibiotic, avoiding certain combinations is key to ensuring its safety and success. Always provide your healthcare provider with a complete list of your medications, including over-the-counter drugs, supplements, and herbal products, before starting treatment. Though common myths about interactions with dairy and most oral contraceptives are unfounded, serious interactions with blood thinners, gout medications, and certain other drugs highlight the importance of medical guidance. By staying informed and communicating openly with your healthcare team, you can manage your treatment effectively and safely.

For more detailed information on drug interactions and medication safety, visit the FDA's official website.

Frequently Asked Questions

While no direct chemical interaction occurs, it is generally recommended to avoid alcohol. Alcohol can worsen common side effects like nausea and diarrhea and can weaken your immune system, which can hinder recovery from your infection.

Despite a long-standing myth, most common antibiotics, including amoxicillin, do not significantly decrease the effectiveness of hormonal birth control pills. However, the antibiotic rifampin is an exception.

Yes, you can consume dairy products like milk and cheese while taking amoxicillin. Unlike some other antibiotics (such as tetracyclines), dairy does not interfere with the absorption of amoxicillin.

Over-the-counter pain relievers like acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) are generally considered safe to take with amoxicillin. Always follow the recommended dosage on the product label.

There are no specific vitamins to avoid, but certain herbal supplements, such as bromelain and guar gum, can interact with amoxicillin absorption. It is always best to inform your doctor or pharmacist about any supplements you are taking.

Amoxicillin can alter gut bacteria that help produce vitamin K, a key blood-clotting factor. This increases the anticoagulant effect of warfarin, raising the risk of excessive bleeding. Your doctor will monitor you closely if you take both medications.

If you are taking both medications and develop a skin rash, contact your healthcare provider immediately. The combination significantly increases the risk of rash, and in rare cases, can signal a severe allergic reaction.