What the FDA labels say about taking them together
Ertapenem and valproic acid
Ertapenem's FDA label of February 4, 2026 names valproic acid in its drug interactions section, and valproic acid's label names ertapenem too. The valproic acid label: “Carbapenem antibiotics may reduce serum valproate concentrations to subtherapeutic levels, resulting in loss of seizure control.”
Check it at the source: the ertapenem FDA label on DailyMed (effective February 4, 2026, Merck Sharp & Dohme LLC); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the ertapenem label say about valproic acid?
Ertapenem label, drug interactionsDRUG INTERACTIONS Co-administration with probenecid inhibits the renal excretion of ertapenem and is therefore not recommended. ( 7.1 ) The concomitant use of ertapenem and valproic acid/divalproex sodium is generally not recommended.
Ertapenem label, warnings and precautionsWARNINGS AND PRECAUTIONS Serious hypersensitivity (anaphylactic) reactions have been reported in patients receiving β-lactams. ( 5.1 ) Seizures and other central nervous system adverse experiences have been reported during treatment. ( 5.2 ) Co-administration of INVANZ with valproic acid or divalproex sodium reduces the serum concentration of valproic acid potentially increasing the risk of breakthrough seizures. ( 5.3 ) Clostridioides difficile -associated diarrhea (ranging from mild diarrhea to fatal colitis):
Source: FDA drug label (INVANZ), Merck Sharp & Dohme LLC, effective February 4, 2026 (SPL set 33f3b99b-fa82-42e0-26bf-f49891ae3d22), via openFDA; the full label on DailyMed
What does the valproic acid label say about ertapenem?
Valproic acid label, drug interactionsCarbapenem Antibiotics A clinically significant reduction in serum valproic acid concentration has been reported in patients receiving carbapenem antibiotics (for example, ertapenem, imipenem, meropenem; this is not a complete list) and may result in loss of seizure control.
Valproic acid label, warnings and precautionsCarbapenem antibiotics (for example, ertapenem, imipenem, meropenem; this is not a complete list) may reduce serum valproate concentrations to subtherapeutic levels, resulting in loss of seizure control.
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
| Ertapenem | Valproic acid | |
|---|---|---|
| Labeled for | Urinary tract infections | Seizures and epilepsy, Migraine |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $26.63 per vial 1 gram vial | $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