What the FDA labels say about taking them together
Cabotegravir and phenobarbital
Cabotegravir's FDA label of April 11, 2025 names phenobarbital in its contraindications section; the phenobarbital labels PlainMeds reads (2) do not name cabotegravir. The cabotegravir label: “Coadministration is contraindicated with VOCABRIA due to potential for loss of efficacy and development of resistance.”
Check it at the source: the cabotegravir FDA label on DailyMed (effective April 11, 2025, ViiV Healthcare Company); the phenobarbital FDA label on DailyMed (effective August 27, 2026).
What does the cabotegravir label say about phenobarbital?
Cabotegravir label, contraindicationsCarbamazepine, oxcarbazepine, phenobarbital, phenytoin o Antimycobacterials: Rifampin, rifapentine Unknown or positive HIV-1 status.
Cabotegravir label, drug interactionsConcomitant Drug Class/Drug Name: Anticonvulsants: Carbamazepine Oxcarbazepine Phenobarbital Phenytoin; Effect on Concentration: ↓Cabotegravir; Clinical Comment: Coadministration is contraindicated with APRETUDE due to potential for significant decreases in plasma concentration of APRETUDE.
Vocabria label (ViiV Healthcare Company, April 11, 2025), contraindicationsCarbamazepine, oxcarbazepine, phenobarbital, phenytoin o Antimycobacterials: Rifampin, rifapentine Prior to initiation of VOCABRIA, note that use of CABENUVA (cabotegravir extended-release injectable suspension; rilpivirine extended-release injectable suspension) with rifabutin is contraindicated.
Vocabria label (ViiV Healthcare Company, April 11, 2025), drug interactionsConcomitant Drug Class/Drug Name: Anticonvulsants: Carbamazepine Oxcarbazepine Phenobarbital Phenytoin; Effect on Concentration: ↓Cabotegravir; Clinical Comment: Coadministration is contraindicated with VOCABRIA due to potential for loss of efficacy and development of resistance [see Contraindications ()].
Source: FDA drug label (Vocabria, NDA212887), ViiV Healthcare Company, effective April 11, 2025 (SPL set 66d450fb-cca4-476c-b0c7-c0730e3e4cf3), via openFDA
Source: FDA drug label (Apretude), ViiV Healthcare Company, effective April 11, 2025 (SPL set 4338428e-43d4-4e02-ac9d-bd98e738a7da), via openFDA; the full label on DailyMed
What does the phenobarbital label say about cabotegravir?
Phenobarbital's label (effective August 27, 2026) and its 1 other brand-application label do not name cabotegravir 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
| Cabotegravir | Phenobarbital | |
|---|---|---|
| Labeled for | HIV | 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