What the FDA labels say about taking them together
Trastuzumab emtansine and voriconazole
Trastuzumab emtansine's FDA label of April 1, 2026 names voriconazole in its drug interactions section; the voriconazole labels PlainMeds reads (3) 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 trastuzumab emtansine FDA label on DailyMed (effective April 1, 2026); the voriconazole FDA label on DailyMed (effective February 26, 2026, Roerig).
What does the trastuzumab emtansine label say about voriconazole?
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
What does the voriconazole label say about trastuzumab emtansine?
Voriconazole's label (effective February 26, 2026) and its 2 other brand-application labels 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 (VFEND), NDA021630 (Pf Prism Cv), as published by Roerig, effective February 26, 2026 (SPL set ce3ef5cf-3087-4d92-9d94-9eb8287228db), 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
| Trastuzumab emtansine | Voriconazole | |
|---|---|---|
| Labeled for | Breast cancer | Fungal infections |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | n/a | $1.88 per tablet 200 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
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