What the FDA labels say about taking them together
Glycerol phenylbutyrate and valproic acid
Glycerol phenylbutyrate's FDA label of October 29, 2025 names valproic acid in its drug interactions section; the valproic acid label PlainMeds reads does not name glycerol phenylbutyrate. The glycerol phenylbutyrate label: “DRUG INTERACTIONS Corticosteroids, valproic acid, or haloperidol: May increase plasma ammonia level; monitor ammonia levels closely.”
Check it at the source: the glycerol phenylbutyrate FDA label on DailyMed (effective October 29, 2025, Horizon Therapeutics USA, Inc.); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the glycerol phenylbutyrate label say about valproic acid?
Glycerol phenylbutyrate label, drug interactionsDRUG INTERACTIONS Corticosteroids, valproic acid, or haloperidol: May increase plasma ammonia level; monitor ammonia levels closely.
Source: FDA drug label (Ravicti), Horizon Therapeutics USA, Inc., effective October 29, 2025 (SPL set 900e7dc0-9afe-4f50-80de-90567bb78519), via openFDA; the full label on DailyMed
What does the valproic acid label say about glycerol phenylbutyrate?
Valproic acid's label (effective January 24, 2025) does not name glycerol phenylbutyrate in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (VALPROIC ACID), PAI Holdings, LLC dba PAI Pharma, effective January 24, 2025 (SPL set 7d5cb52e-37dd-4dfa-a6f4-09f9548846c6), 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
| Glycerol phenylbutyrate | Valproic acid | |
|---|---|---|
| Labeled for | n/a | Seizures and epilepsy, Migraine |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | n/a | $0.243 per capsule 250 mg capsule |
| Shortage now | A presentation being discontinued | Listed; available |
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