What the FDA labels say about taking them together
Carmustine and phenobarbital
Carmustine's FDA label of April 9, 2026 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name carmustine. The carmustine label: “DRUG INTERACTIONS Cimetidine: Increased myelosuppression with concomitant use. Phenobarbital: Induces carmustine metabolism, reducing exposure.”
Check it at the source: the carmustine FDA label on DailyMed (effective April 9, 2026, Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the carmustine label say about phenobarbital?
Carmustine label, drug interactionsDRUG INTERACTIONS Cimetidine: Increased myelosuppression with concomitant use. (7.1) Phenobarbital: Induces carmustine metabolism, reducing exposure.
Source: FDA drug label (CARMUSTINE), Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., effective April 9, 2026 (SPL set b9b47082-32ee-4abb-a7b2-52292894d3f8), via openFDA; the full label on DailyMed
What does the phenobarbital label say about carmustine?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name carmustine 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
| Carmustine | Phenobarbital | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Seizures and epilepsy |
| Boxed warning | Yes | 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