Allopurinol and Didanosine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Allopurinol
Didanosine
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased serum concentrations of didanosine
Interaction Deep Dive
The didanosine area under the concentration-time curve (AUC) was increased approximately 4-fold when allopurinol 300 mg daily was coadministered with a single dose of didanosine 200 mg to two patients with renal impairment. It is unknown if a similar interaction would occur in patients with normal renal function. Coadministration of didanosine and allopurinol is contraindicated21.
Why it happens (mechanism)
Increased didanosine bioavailability
Literature reports
1 report — tap to read
a) Two renally impaired patients received allopurinol 300 mg daily and didanosine 200 mg as a single dose. Steady-state area under the concentration-time curve (AUC) for didanosine increased 312%. Maximum serum concentration (Cmax) of didanosine increased 232%. Fourteen healthy volunteers received allopurinol 300 mg daily for seven days and didanosine 400 mg as a single dose. Steady-state AUC for didanosine increased 113% and Cmax of didanosine increased 69% 21.
Common questions
Can I take Allopurinol and Didanosine together?
Increased serum concentrations of didanosine Always confirm with your pharmacist or prescriber before making any change.
How serious is the Allopurinol and Didanosine interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Allopurinol or Didanosine need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (2)
- Product Information: VIDEX EC(R) delayed release oral capsules, enteric coated beadlets, didanosine delayed release oral capsules, enteric coated beadlets. Bristol-Myers Squibb Company, Princeton, NJ, 2009.
- Product Information: VIDEX(R) pediatric powder for oral solution, didanosine pediatric powder for oral solution. Bristol-Myers Squibb Company, Princeton, NJ, 2009.
Keep reading about Allopurinol
Keep reading about Didanosine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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