What the FDA labels say about taking them together
Cilastatin/imipenem and valproic acid
Cilastatin/imipenem's FDA label of July 5, 2024 names valproic acid in its drug interactions section; the valproic acid label PlainMeds reads does not name cilastatin/imipenem. The cilastatin/imipenem label: “Valproic acid/divalproex sodium: Concomitant use with PRIMAXIN is generally not recommended.”
Check it at the source: the cilastatin/imipenem FDA label on DailyMed (effective July 5, 2024, Merck Sharp & Dohme LLC); the valproic acid FDA label on DailyMed (effective January 24, 2025, PAI Holdings, LLC dba PAI Pharma).
What does the cilastatin/imipenem label say about valproic acid?
Cilastatin/imipenem label, drug interactionsValproic acid/divalproex sodium: Concomitant use with PRIMAXIN is generally not recommended.
Cilastatin/imipenem label, warnings and precautionsIncreased Seizure Potential Due to Interaction with Valproic Acid: Co-administration of PRIMAXIN, to patients receiving valproic acid or divalproex sodium results in a reduction in valproic acid concentrations.
Source: FDA drug label (PRIMAXIN IV), Merck Sharp & Dohme LLC, effective July 5, 2024 (SPL set f41d8abd-7792-4918-1b93-bd83ea01955e), via openFDA; the full label on DailyMed
What does the valproic acid label say about cilastatin/imipenem?
Valproic acid's label (effective January 24, 2025) does not name cilastatin/imipenem 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
| Cilastatin/imipenem | Valproic acid | |
|---|---|---|
| Labeled for | Bacterial infections, Urinary tract infections | 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