What the FDA labels say about taking them together
Darunavir and phenobarbital
Darunavir's FDA label of August 29, 2025 names phenobarbital in its drug interactions section; the phenobarbital labels PlainMeds reads (2) do not name darunavir. The darunavir label: “Phenytoin and phenobarbital levels should be monitored when co-administering with PREZISTA/ritonavir.”
Check it at the source: the darunavir FDA label on DailyMed (effective August 29, 2025, Janssen Products LP); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the darunavir label say about phenobarbital?
Darunavir label, drug interactionsConcomitant Drug Class Drug Name Examples: phenobarbital, phenytoin; Effect on Concentration of Darunavir Or Concomitant Drug: ↔ darunavir ↓ phenytoin ↓ phenobarbital; Clinical Comment: Phenytoin and phenobarbital levels should be monitored when co-administering with PREZISTA/ritonavir.
Source: FDA drug label (PREZISTA), Janssen Products LP, effective August 29, 2025 (SPL set 814301f9-c990-46a5-b481-2879a521a16f), via openFDA; the full label on DailyMed
What does the phenobarbital label say about darunavir?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name darunavir 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
| Darunavir | Phenobarbital | |
|---|---|---|
| Labeled for | HIV | Seizures and epilepsy |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.16 per tablet 600 mg tablet | $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