What the FDA labels say about taking them together
Ketoconazole and lapatinib ditosylate
Lapatinib ditosylate's FDA label of November 30, 2023 names ketoconazole in its drug interactions section; the ketoconazole label PlainMeds reads does not name lapatinib ditosylate. The lapatinib ditosylate label: “Inhibit or Induce Cytochrome P450 3A4 Enzymes Lapatinib undergoes extensive metabolism by CYP3A4, and concomitant administration of strong inhibitors or inducers of CYP3A4 alter lapatinib concentrations significantly.”
Check it at the source: the ketoconazole FDA label on DailyMed (effective January 28, 2026, E. Fougera & Co. a division of Fougera Pharmaceuticals, LLC); the lapatinib ditosylate FDA label on DailyMed (effective November 30, 2023, Teva Pharmaceuticals, Inc.).
What does the ketoconazole label say about lapatinib ditosylate?
Ketoconazole's label (effective January 28, 2026) does not name lapatinib ditosylate 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
What does the lapatinib ditosylate label say about ketoconazole?
Lapatinib ditosylate label, drug interactionsInhibit or Induce Cytochrome P450 3A4 Enzymes Lapatinib undergoes extensive metabolism by CYP3A4, and concomitant administration of strong inhibitors or inducers of CYP3A4 alter lapatinib concentrations significantly (see Ketoconazole and Carbamazepine sections, below).
Source: FDA drug label (Lapatinib), Teva Pharmaceuticals, Inc., effective November 30, 2023 (SPL set b09abf73-1eef-4e12-b400-c030d546d223), 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
| Ketoconazole | Lapatinib ditosylate | |
|---|---|---|
| Labeled for | Fungal infections | Breast cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.249 per gram 2% cream | n/a |
| 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