What the FDA labels say about taking them together
Metronidazole and quinidine
Metronidazole's FDA label (Metronidazole) of June 12, 2025 names quinidine in its drug interactions section; the quinidine label PlainMeds reads does not name metronidazole. The metronidazole label: “Cytochrome P450 3A4 (CYP3A4) substrates Concomitant use of Metronidazole Injection and CYP3A4 substrates may increase respective CYP3A4-substrate plasma levels.”
Check it at the source: the metronidazole FDA label on DailyMed (effective September 3, 2024, Aurobindo Pharma Limited); the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.).
What does the metronidazole label say about quinidine?
Metronidazole label (Baxter Healthcare Corporation, June 12, 2025), drug interactionsCytochrome P450 3A4 (CYP3A4) substrates Concomitant use of Metronidazole Injection and CYP3A4 substrates (e.g., amiodarone, tacrolimus, cyclosporine, carbamazepine, phenytoin, and quinidine) may increase respective CYP3A4-substrate plasma levels.
Source: FDA drug label (Metronidazole, NDA018657), Baxter Healthcare Corporation, effective June 12, 2025 (SPL set d2112f37-5080-4a19-bcc3-6386b49abe1d), via openFDA
Source: FDA drug label (Metronidazole), Aurobindo Pharma Limited, effective September 3, 2024 (SPL set f68397ee-67db-472e-8607-4300064e37df), via openFDA; the full label on DailyMed
What does the quinidine label say about metronidazole?
Quinidine's label (effective February 1, 2018) does not name metronidazole 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
| Metronidazole | Quinidine | |
|---|---|---|
| Labeled for | Bacterial infections | Atrial fibrillation |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.102 per tablet 250 mg tablet | $4.92 per tablet 324 mg tablet |
| Shortage now | In shortage | 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