Allopurinol and Amoxicillin interaction
Allopurinol and Amoxicillin: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Allopurinol label · effective 2026-05-21
Concomitant use of the following drugs may also increase the risk of skin rash, which may be severe: bendamustine, ampicillin and amoxicillin [ see Drug Interactions (7.1) ].
The following drugs may increase the risk of serious skin reactions: bendamustine, thiazide diuretics, ampicillin and amoxicillin.
Drugs Known to Affect the Occurrence of Skin Rash and Hypersensitivity Concomitant use of the following drugs may increase the risk of skin rash, which may be severe: bendamustine, thiazide diuretics, ampicillin and amoxicillin.
From the Amoxicillin label · effective 2026-07-07
Co-administration with allopurinol increases the risk of rash.
Allopurinol The concurrent administration of allopurinol and amoxicillin increases the incidence of rashes in patients receiving both drugs as compared to patients receiving amoxicillin alone.
It is not known whether this potentiation of rashes is due to allopurinol or the hyperuricemia present in these patients.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.