What the FDA labels say about taking them together
Istradefylline and ketoconazole
Istradefylline's FDA label of May 20, 2025 names ketoconazole in its drug interactions section; the ketoconazole label PlainMeds reads does not name istradefylline. The istradefylline label: “Drugs on NOURIANZ Strong CYP3A4 Inhibitors Coadministration of NOURIANZ with a strong CYP3A4 inhibitor (ketoconazole) increased istradefylline AUC inf by 2.5-fold.”
Check it at the source: the istradefylline FDA label on DailyMed (effective May 20, 2025, Kyowa Kirin, Inc.); the ketoconazole FDA label on DailyMed (effective January 28, 2026, E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC).
What does the istradefylline label say about ketoconazole?
Istradefylline label, drug interactionsDrugs on NOURIANZ Strong CYP3A4 Inhibitors Coadministration of NOURIANZ with a strong CYP3A4 inhibitor (ketoconazole) increased istradefylline AUC inf by 2.5-fold [see Clinical Pharmacology (12.3) ].
Source: FDA drug label (NOURIANZ), Kyowa Kirin, Inc., effective May 20, 2025 (SPL set a7d008cb-b273-4049-a5d2-9c6902910d58), via openFDA; the full label on DailyMed
What does the ketoconazole label say about istradefylline?
Ketoconazole's label (effective January 28, 2026) does not name istradefylline in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (ketoconazole), E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC, effective January 28, 2026 (SPL set cad7c647-34a9-4e4e-83b3-8d78e58f588f), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Istradefylline | Ketoconazole | |
|---|---|---|
| Labeled for | Parkinson's disease | Fungal infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.249 per gram 2% cream |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once