What the FDA labels say about taking them together
Sodium benzoate/sodium phenylacetate and valproic acid
Sodium benzoate/sodium phenylacetate's FDA label of December 6, 2025 names valproic acid in its drug interactions section; the valproic acid label PlainMeds reads does not name sodium benzoate/sodium phenylacetate. The sodium benzoate/sodium phenylacetate label: “… Probenecid may affect renal excretion of phenylacetylglutamine and hippurate. Valproic acid given to patients with urea cycle disorders may exacerbate their condition and antagonize the efficacy of Sodium Phenylacetate …”
Check it at the source: the sodium benzoate/sodium phenylacetate FDA label on DailyMed (effective December 6, 2025); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the sodium benzoate/sodium phenylacetate label say about valproic acid?
Sodium benzoate/sodium phenylacetate label, drug interactionsDRUG INTERACTIONS Some antibiotics such as penicillin may affect the overall disposition of the infused drug. ( 7 ) Probenecid may affect renal excretion of phenylacetylglutamine and hippurate. ( 7 ) Valproic acid given to patients with urea cycle disorders may exacerbate their condition and antagonize the efficacy of Sodium Phenylacetate and Sodium Benzoate Injection through inhibition of the synthesis of N-acetylglutamate, a co-factor for carbamyl phosphate synthetase. ( 7 ) Use of corticosteroids may cause the breakdown of body protein and potentially increase plasma ammonia levels in patients with impaired ability to form urea. …
Sodium Phenylacetate And Sodium Benzoate label (MAIA PHARMACEUTICALS, January 16, 2023), drug interactionsThere have been reports that valproic acid can induce hyperammonemia through inhibition of the synthesis of N-acetylglutamate, a co-factor for carbamyl phosphate synthetase.
Source: FDA drug label (Sodium Phenylacetate And Sodium Benzoate, NDA215025), MAIA PHARMACEUTICALS, effective January 16, 2023 (SPL set ab40b62b-9f8d-4394-92d5-09d9f1941eaa), via openFDA
Source: FDA drug label (Sodium phenylacetate and Sodium benzoate), Navinta LLC, effective December 6, 2025 (SPL set d20768fe-4516-483a-a082-ff1df9ad1d99), via openFDA; the full label on DailyMed
What does the valproic acid label say about sodium benzoate/sodium phenylacetate?
Valproic acid's label (effective January 24, 2025) does not name sodium benzoate/sodium phenylacetate 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
| Sodium benzoate/sodium phenylacetate | 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 | No current entry | 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