What the FDA labels say about taking them together
Phenobarbital and sofosbuvir
Sofosbuvir's FDA label of December 26, 2024 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name sofosbuvir. The sofosbuvir label: “Coadministration of SOVALDI with carbamazepine, phenytoin, phenobarbital or oxcarbazepine is expected to decrease the concentration of sofosbuvir, leading to reduced therapeutic effect of SOVALDI. …”
Check it at the source: the phenobarbital FDA label on DailyMed (effective August 27, 2026); the sofosbuvir FDA label on DailyMed (effective December 26, 2024, Gilead Sciences, Inc.).
What does the phenobarbital label say about sofosbuvir?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name sofosbuvir 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
What does the sofosbuvir label say about phenobarbital?
Sofosbuvir label, drug interactionsConcomitant Drug Class/Drug Name: Anticonvulsants: Carbamazepine phenytoin phenobarbital oxcarbazepine; Effect on Concentration ↓ = decrease.: ↓ sofosbuvir ↓ GS-331007; Clinical Comment: Coadministration of SOVALDI with carbamazepine, phenytoin, phenobarbital or oxcarbazepine is expected to decrease the concentration of sofosbuvir, leading to reduced therapeutic effect of SOVALDI. Coadministration is not recommended.
Source: FDA drug label (Sovaldi), Gilead Sciences, Inc., effective December 26, 2024 (SPL set 80beab2c-396e-4a37-a4dc-40fdb62859cf), 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
| Phenobarbital | Sofosbuvir | |
|---|---|---|
| Labeled for | Seizures and epilepsy | Hepatitis C |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.213 per tablet 100 mg tablet | 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