Allopurinol and Famciclovir Interaction
Drug interaction information between Allopurinol and Famciclovir.
Allopurinol and Famciclovir have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Allopurinol and Famciclovir. 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
These two drugs do not have a meaningful effect on how the body breaks down or uses either medicine.
FDA Label Information
7.2 Potential for Other Drugs to Affect Penciclovir No clinically significant alterations in penciclovir pharmacokinetics were observed following single-dose administration of 500 mg famciclovir after pretreatment with multiple doses of allopurinol, cimetidine, theophylline, zidovudine, promethazine, when given shortly after an antacid (magnesium and aluminum hydroxide), or concomitantly with emtricitabine.
Allopurinol Also Interacts With
- Pegloticase major
- Cyclosporine moderate
- Amoxicillin moderate
- Amoxicillin/Clavulanate moderate
- Warfarin minor
Famciclovir Also Interacts With
- Digoxin minor
- Probenecid minor
- Theophylline minor
- Cimetidine minor
- Promethazine minor
Frequently Asked Questions
What SPL severity band is on file for Allopurinol + Famciclovir?
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 Famciclovir's 7. In the minor band specifically: Allopurinol has 6 (also Warfarin, Theophylline, Ampicillin/Sulbactam, Prazosin); Famciclovir has 7 (also Digoxin, Probenecid, Theophylline, Cimetidine).
What mechanism field is on file for Allopurinol and Famciclovir?
These two drugs do not have a meaningful effect on how the body breaks down or uses either medicine.
Allopurinol carries more major-labeled pairs than Famciclovir
SPL source-record counts only. This page's band is minor · classes on file: Allopurinol (Xanthine Oxidase Inhibitor); Famciclovir (Antiviral (Nucleoside Analog)).
Allopurinol has 1 major-labeled pair vs Famciclovir's 0. This page itself is in the minor band, not the major band.
1 major · 3 moderate · 6 minor · 10 total
- Other minor peers for Allopurinol
- Warfarin
- Theophylline
- Ampicillin/Sulbactam
- Prazosin
0 major · 0 moderate · 7 minor · 7 total
- Other minor peers for Famciclovir
- Digoxin
- Probenecid
- Theophylline
- Cimetidine
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.