Atazanavir and Didanosine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Atazanavir
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
Reduced solubility and exposure to atazanavir with the didanosine buffered formulation and reduced didanosine exposure with enteric coated didanosine formulation
Interaction Deep Dive
Atazanavir solubility decreases as gastric pH increases. Exposure to atazanavir was markedly decreased when atazanavir and didanosine buffered tablets were coadministered. The decrease in exposure to atazanavir is likely due to the increase in gastric pH caused by buffers in the didanosine tablets. Didanosine enteric coated capsules simultaneously administered with atazanavir decreases didanosine exposure. Atazanavir should be given with food 2 hours before or 1 hour after didanosine buffered formulation or enteric-coated capsules1.
Why it happens (mechanism)
An unknown mechanism when administered with enteric coated didanosine; increase in gastric pH caused by buffers in the didanosine buffered formulation tablets
Literature reports
2 reports — tap to read
a) Simultaneous coadministration of didanosine buffered tablets with an atazanavir appeared to significantly reduce the serum plasma level of atazanavir. Didanosine buffered tablets 200 mg plus stavudine 40 mg administered simultaneously with atazanavir 400 mg once daily in 31 subjects resulted in a significant decline in Cmax, AUC and Cmin by 89%, 87% and 84% respectively 1.
b) Simultaneous coadministration of atazanavir and didanosine enteric coated capsules significantly decreased the serum plasma levels of didanosine. Didanosine 400 mg given administered simultaneously with atazanavir 400 mg once daily with food resulted in a decline in Cmax and AUC by 36% and 34%, respectively and an increase in Cmin by 13%. Alternatively, didanosine 400 mg given with or without food once daily administered simultaneously with atazanavir 300 mg plus ritonavir 100 mg once daily resulted in a decline in Cmax and AUC by 38% and 34%, respectively and an increase in Cmin by 25% 1.
Common questions
Can I take Atazanavir and Didanosine together?
Reduced solubility and exposure to atazanavir with the didanosine buffered formulation and reduced didanosine exposure with enteric coated didanosine formulation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Atazanavir and Didanosine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
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 Atazanavir 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 (1)
- Product Information: REYATAZ(R) oral capsules, oral powder, atazanavir oral capsules, oral powder. Bristol-Myers Squibb Company (per FDA), Princeton, NJ, 2020. DailyMed
Keep reading about Atazanavir
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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