What the FDA labels say about taking them together
Cabozantinib and phenobarbital
Cabozantinib's FDA label (Cometriq) of October 18, 2025 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name cabozantinib. The cabozantinib label: “Avoid chronic co-administration of strong CYP3A4 inducers with COMETRIQ or increase the dosage of COMETRIQ if concomitant use with strong CYP3A4 inducers cannot be avoided.”
Check it at the source: the cabozantinib FDA label on DailyMed (effective October 19, 2025, Exelixis, Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the cabozantinib label say about phenobarbital?
Cometriq label (Exelixis, Inc., October 18, 2025), drug interactionsAvoid chronic co-administration of strong CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin, rifabutin, rifapentine, phenobarbital, St. John’s Wort) with COMETRIQ or increase the dosage of COMETRIQ if concomitant use with strong CYP3A4 inducers cannot be avoided [see Dosage and Administration ( 2.2 ), Clinical Pharmacology ( 12.3 )].
Source: FDA drug label (Cometriq, NDA203756), Exelixis, Inc., effective October 18, 2025 (SPL set 1a0c3bea-c87b-4d25-bb44-5f0174da6b34), via openFDA
Source: FDA drug label (CABOMETYX), Exelixis, Inc., effective October 19, 2025 (SPL set 3850cce2-6137-42e5-a792-d318c4a4b3b5), via openFDA; the full label on DailyMed
What does the phenobarbital label say about cabozantinib?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name cabozantinib in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Phenobarbital), Chartwell RX, LLC, effective August 27, 2026 (SPL set 74428144-fb24-40a5-a670-3b876e2d116c), 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
| Cabozantinib | Phenobarbital | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.213 per tablet 100 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