Ampicillin/Sulbactam and Allopurinol Interaction
Drug interaction information between Ampicillin/Sulbactam and Allopurinol.
Ampicillin/Sulbactam and Allopurinol have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Ampicillin/Sulbactam and Allopurinol. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Taking these two medicines at the same time significantly increases your chances of developing a skin rash.
FDA Label Information
The concurrent administration of allopurinol and ampicillin increases substantially the incidence of rashes in patients receiving both drugs as compared to patients receiving ampicillin alone. It is not known whether this potentiation of ampicillin rashes is due to allopurinol or the hyperuricemia present in these patients. There are no data with UNASYN and allopurinol administered concurrently.
Ampicillin/Sulbactam Also Interacts With
- Probenecid minor
Allopurinol Also Interacts With
- Pegloticase major
- Cyclosporine moderate
- Amoxicillin moderate
- Amoxicillin/Clavulanate moderate
- Warfarin minor
Frequently Asked Questions
What SPL severity band is on file for Ampicillin/Sulbactam + Allopurinol?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Allopurinol has 10 labeled pairs on file vs Ampicillin/Sulbactam's 2. In the minor band specifically: Ampicillin/Sulbactam has 2 (also Probenecid); Allopurinol has 6 (also Warfarin, Theophylline, Famciclovir, Prazosin).
What mechanism field is on file for Ampicillin/Sulbactam and Allopurinol?
Taking these two medicines at the same time significantly increases your chances of developing a skin rash.
Allopurinol carries more major-labeled pairs than Ampicillin/Sulbactam
SPL source-record counts only. This page's band is minor · classes on file: Ampicillin/Sulbactam (Penicillin / Beta-Lactamase Inhibitor); Allopurinol (Xanthine Oxidase Inhibitor).
Allopurinol has 1 major-labeled pair vs Ampicillin/Sulbactam's 0. This page itself is in the minor band, not the major band.
0 major · 0 moderate · 2 minor · 2 total
- Other minor peers for Ampicillin/Sulbactam
- Probenecid
1 major · 3 moderate · 6 minor · 10 total
- Other minor peers for Allopurinol
- Warfarin
- Theophylline
- Famciclovir
- Prazosin
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.