What the FDA labels say about taking them together
Nirmatrelvir/ritonavir and primidone
Nirmatrelvir/ritonavir's FDA label of February 19, 2026 names primidone in its contraindications section; the primidone label PlainMeds reads does not name nirmatrelvir/ritonavir. The nirmatrelvir/ritonavir label: “Co-administration contraindicated due to potential loss of virologic response and possible resistance.”
Check it at the source: the nirmatrelvir/ritonavir FDA label on DailyMed (effective February 19, 2026, Pfizer Laboratories Div Pfizer Inc); the primidone FDA label on DailyMed (effective September 10, 2026, Bausch Health US, LLC).
What does the nirmatrelvir/ritonavir label say about primidone?
Nirmatrelvir/ritonavir label, contraindicationsAnticonvulsant: carbamazepine, phenobarbital, primidone, phenytoin
Nirmatrelvir/ritonavir label, drug interactionsDrug Class: Anticonvulsants; Drugs within Class: carbamazepine, phenobarbital, primidone, phenytoin; Effect on Concentration: ↓ nirmatrelvir/ritonavir; Clinical Comments: Co-administration contraindicated due to potential loss of virologic response and possible resistance [see ].
Source: FDA drug label (Paxlovid), Pfizer Laboratories Div Pfizer Inc, effective February 19, 2026 (SPL set 8a99d6d6-fd9e-45bb-b1bf-48c7f761232a), via openFDA; the full label on DailyMed
What does the primidone label say about nirmatrelvir/ritonavir?
Primidone's label (effective September 10, 2026) does not name nirmatrelvir/ritonavir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Mysoline), NDA009170 (Valeant), as published by Bausch Health US, LLC, effective September 10, 2026 (SPL set af593171-dabb-4ea3-b44c-89ed457b2c46), 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
| Nirmatrelvir/ritonavir | Primidone | |
|---|---|---|
| Labeled for | COVID-19 | Seizures and epilepsy |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $49.24 per unit 300-100 mg dose pack | $0.0914 per tablet 50 mg tablet |
| 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