What the FDA labels say about taking them together
Diazepam and quinidine
Diazepam's FDA label (Valtoco) of June 3, 2026 names quinidine in its drug interactions section; the quinidine label PlainMeds reads does not name diazepam. The diazepam label: “Inhibitors of CYP2C19 and CYP3A4 Inhibitors of CYP2C19 and CYP3A4 could decrease the rate of diazepam elimination; therefore, adverse reactions to VALTOCO may be increased.”
Check it at the source: the diazepam FDA label on DailyMed (effective August 11, 2026, Waylis Therapuetics LLC); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the diazepam label say about quinidine?
Valtoco label (Neurelis, Inc, June 3, 2026), drug interactionsInhibitors of CYP2C19 and CYP3A4 Inhibitors of CYP2C19 (e.g., cimetidine, quinidine, and tranylcypromine) and CYP3A4 (e.g., ketoconazole, troleandomycin, and clotrimazole) could decrease the rate of diazepam elimination; therefore, adverse reactions to VALTOCO may be increased.
Source: FDA drug label (Valtoco, NDA211635), Neurelis, Inc, effective June 3, 2026 (SPL set 1a8bcc90-68fa-474d-832c-0df01e825f39), via openFDA
Source: FDA drug label (Valium), Waylis Therapuetics LLC, effective August 11, 2026 (SPL set 260e2041-2bb3-482f-850e-b5d47a7bdbe6), via openFDA; the full label on DailyMed
What does the quinidine label say about diazepam?
Quinidine's label (effective February 1, 2018) does not name diazepam in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Quinidine Gluconate), Sun Pharmaceutical Industries, Inc., effective February 1, 2018 (SPL set 5023f053-fcc4-4c2c-aa59-9ec198ad185e), 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
| Diazepam | Quinidine | |
|---|---|---|
| Labeled for | Anxiety, Muscle spasms and spasticity | Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.0283 per tablet 10 mg tablet | $4.92 per tablet 324 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