What the FDA labels say about taking them together
Isavuconazonium and ketoconazole
Isavuconazonium's FDA label of April 25, 2025 names ketoconazole in its contraindications section; the ketoconazole label PlainMeds reads does not name isavuconazonium. The isavuconazonium label: “Ketoconazole; Comments: Contraindicate coadministration of all potent CYP3A4 inhibitors; There is more than a 5-fold increase in exposure of isavuconazole upon coadministration with ketoconazole.”
Check it at the source: the isavuconazonium FDA label on DailyMed (effective April 25, 2025, Astellas Pharma US, Inc.); the ketoconazole FDA label on DailyMed (effective January 28, 2026, E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC).
What does the isavuconazonium label say about ketoconazole?
Isavuconazonium label, contraindicationsCoadministration of strong CYP3A4 inhibitors, such as ketoconazole or high-dose ritonavir (400 mg every 12 hours), with CRESEMBA is contraindicated because strong CYP3A4 inhibitors can significantly increase the plasma concentration of isavuconazole [see Drug Interactions ( 7 ) and Clinical Pharmacology ( 12.3 )].
Isavuconazonium label, drug interactionsRecommendation: Ketoconazole; Comments: Contraindicate coadministration of all potent CYP3A4 inhibitors; There is more than a 5-fold increase in exposure of isavuconazole upon coadministration with ketoconazole [see ()].
Isavuconazonium label, warnings and precautionsCoadministration of CRESEMBA with strong CYP3A4 inhibitors such as ketoconazole or high-dose ritonavir and strong CYP3A4 inducers such as rifampin, carbamazepine, St. John’s wort, or long acting barbiturates is contraindicated [see Contraindications ( 4 ) and Drug Interactions ( 7 )].
Source: FDA drug label (CRESEMBA), Astellas Pharma US, Inc., effective April 25, 2025 (SPL set 8f7f73b8-586a-4df0-935f-fecd4696c16c), via openFDA; the full label on DailyMed
What does the ketoconazole label say about isavuconazonium?
Ketoconazole's label (effective January 28, 2026) does not name isavuconazonium 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
| Isavuconazonium | Ketoconazole | |
|---|---|---|
| Labeled for | n/a | Fungal infections |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $114.00 per capsule 186 mg capsule | $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