What the FDA labels say about taking them together
Cabotegravir and phenytoin
Cabotegravir's FDA label of April 11, 2025 names phenytoin in its contraindications section; the phenytoin 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 phenytoin FDA label on DailyMed (effective October 15, 2024, Mylan Pharmaceuticals Inc.).
What does the cabotegravir label say about phenytoin?
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 phenytoin label say about cabotegravir?
Phenytoin's label (effective October 15, 2024) 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 (Phenytek), Mylan Pharmaceuticals Inc., effective October 15, 2024 (SPL set 0f94c791-8b07-4b41-927e-c9f28bec5f60), 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 | Phenytoin | |
|---|---|---|
| Labeled for | HIV | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | n/a | $0.145 per capsule 100 mg capsule |
| Shortage now | No current entry | 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