Didanosine and Nalidixic Acid: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Didanosine
Nalidixic Acid
No brand names on record
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
Decreased nalidixic acid serum concentrations by buffered didanosine preparations
Interaction Deep Dive
Formulations of didanosine that contain divalent and trivalent cations, such as the chewable/buffered tablets and the pediatric powder for oral solution, may form chelation complexes with nalidixic acid and interfere with its bioavailability. Nalidixic acid should be administered at least two hours before or two hours after such formulations of didanosine1.
Why it happens (mechanism)
Inhibition of nalidixic acid absorption/bioavailability
Common questions
Can I take Didanosine and Nalidixic Acid together?
Decreased nalidixic acid serum concentrations by buffered didanosine preparations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Didanosine and Nalidixic Acid interaction?
It is rated moderate. Can be significant — usually manageable with 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Didanosine or Nalidixic Acid 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: NegGram(R) oral caplets, nalidixic acid oral caplets. Sanofi-Aventis, Bridgewater, NJ, 2008. DailyMed
Keep reading about Didanosine
Keep reading about Nalidixic Acid
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