Istradefylline and Clarithromycin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Clarithromycin
Istradefylline
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 istradefylline exposure
Interaction Deep Dive
Coadministration of istradefylline with a strong CYP3A4 inhibitor increases istradefylline exposure and risk for adverse effects. Coadministration of ketoconazole (strong CYP3A4 inhibitor) with istradefylline increased the AUC of istradefylline by 2.5-fold, but had no effect on Cmax. During concomitant use, the maximum dose of istradefylline is 20 mg orally once daily1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of istradefylline
Literature reports
1 report — tap to read
a) Coadministration of ketoconazole (strong CYP3A4 inhibitor) 200 mg twice daily for 4 days with a single dose of istradefylline 40 mg increased the AUC(infinity) of istradefylline by 2.5-fold, but had no effect on Cmax 1.
Common questions
Can I take Istradefylline and Clarithromycin together?
Increased istradefylline exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Istradefylline and Clarithromycin 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Istradefylline or Clarithromycin 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: NOURIANZ(TM) oral tablets, istradefylline oral tablets. Kyowa Kirin Inc (per FDA), Bedminster, NJ, 2019. DailyMed
Keep reading about Clarithromycin
Keep reading about Istradefylline
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist