Antibiotics Home > Drugs That Can Interfere With Amoxicillin

Allopurinol (Aloprim, Zyloprim)
Combining allopurinol with amoxicillin increases the risk of skin rashes or other allergic reactions. Check with your healthcare provider before taking these medications together.
Birth Control Pills
Despite the longstanding belief that antibiotics interact with birth control pills, several studies have shown that almost all antibiotics do not increase the risk of pregnancy in women taking birth control pills. Nevertheless, there have been reports of birth control pill failure in women who have taken antibiotics. Ask your healthcare provider about whether or not you need a backup method of birth control.
Certain Other Antibiotics
Theoretically, certain other antibiotics may make amoxicillin less effective. Check with your healthcare provider before taking such medications together.
Methotrexate (Rheumatrex, Trexall)
Penicillin-type antibiotics (including amoxicillin) may decrease the body's ability to remove methotrexate, leading to high blood levels of methotrexate. Your healthcare provider may need to monitor your more closely.
Oral Typhoid Vaccine
Amoxicillin may decrease the effectiveness of the oral typhoid vaccine. If you have taken amoxicillin recently or are currently taking amoxicillin, your oral typhoid vaccine may need to be postponed for at least a day after taking amoxicillin.
Probenecid (Benuryl)
Probenecid can decrease the body's ability to remove amoxicillin from the blood, potentially leading to high amoxicillin blood levels. Talk with your healthcare provider before taking these medications together.
There have been reports of increased international normalized ratio (INR) in people taking amoxicillin with warfarin, indicating that amoxicillin may increase the risk of bleeding with warfarin. Check with your healthcare provider before taking these medications together. More frequent INR monitoring, and sometimes even warfarin dosage adjustments, might be necessary.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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