What the FDA labels say about taking them together
Itraconazole and trastuzumab emtansine
Trastuzumab emtansine's FDA label of April 1, 2026 names itraconazole in its drug interactions section; the itraconazole labels PlainMeds reads (2) do not name trastuzumab emtansine. The trastuzumab emtansine label: “Concomitant use of strong CYP3A4 inhibitors with KADCYLA should be avoided due to the potential for an increase in DM1 exposure and toxicity.”
Check it at the source: the itraconazole FDA label on DailyMed (effective July 13, 2026, Janssen Pharmaceuticals, Inc.); the trastuzumab emtansine FDA label on DailyMed (effective April 1, 2026).
What does the itraconazole label say about trastuzumab emtansine?
Itraconazole's label (effective July 13, 2026) and its 1 other brand-application label do not name trastuzumab emtansine in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (SPORANOX), Janssen Pharmaceuticals, Inc., effective July 13, 2026 (SPL set a4d555fa-787c-40fb-bb7d-b0d4f7318fd0), via openFDA; the full label on DailyMed
What does the trastuzumab emtansine label say about itraconazole?
Trastuzumab emtansine label, drug interactionsConcomitant use of strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, atazanavir, indinavir, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin, and voriconazole) with KADCYLA should be avoided due to the potential for an increase in DM1 exposure and toxicity.
Source: FDA drug label (KADCYLA), Genentech, Inc., effective April 1, 2026 (SPL set 23f3c1f4-0fc8-4804-a9e3-04cf25dd302e), 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
| Itraconazole | Trastuzumab emtansine | |
|---|---|---|
| Labeled for | Fungal infections | Breast cancer |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.910 per capsule 100 mg capsule | n/a |
| Shortage now | A presentation being discontinued | 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