What the FDA labels say about taking them together
Cimetidine and metronidazole
Cimetidine's FDA label of July 15, 2026 names metronidazole in its drug interactions section, and metronidazole's label names cimetidine too. The cimetidine label: “… diazepam, certain tricyclic antidepressants, lidocaine, theophylline, and metronidazole, thereby delaying elimination and increasing blood levels of these drugs.”
Check it at the source: the cimetidine FDA label on DailyMed (effective July 15, 2026, Mylan Pharmaceuticals Inc.); the metronidazole FDA label on DailyMed (effective September 3, 2024, Aurobindo Pharma Limited).
What does the cimetidine label say about metronidazole?
Cimetidine label, drug interactionsDrug Interactions Cimetidine tablets, apparently through an effect on certain microsomal enzyme systems, has been reported to reduce the hepatic metabolism of warfarin-type anticoagulants, phenytoin, propranolol, nifedipine, chlordiazepoxide, diazepam, certain tricyclic antidepressants, lidocaine, theophylline, and metronidazole, thereby delaying elimination and increasing blood levels of these drugs.
Source: FDA drug label (Cimetidine), Mylan Pharmaceuticals Inc., effective July 15, 2026 (SPL set 06c0a509-026f-44e0-9975-a94a8de51d43), via openFDA; the full label on DailyMed
What does the metronidazole label say about cimetidine?
Metronidazole label, drug interactionsDrugs that Inhibit CYP450 Enzymes The simultaneous administration of drugs that decrease microsomal liver enzyme activity, such as cimetidine, may prolong the half-life and decrease plasma clearance of metronidazole.
Source: FDA drug label (Metronidazole, NDA018900), B. Braun Medical Inc., effective April 23, 2026 (SPL set fd191c06-9d3b-4e46-9f79-90f6af614947), via openFDA
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
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
| Cimetidine | Metronidazole | |
|---|---|---|
| Labeled for | Acid reflux and ulcers | Bacterial infections |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.236 per tablet 300 mg tablet | $0.102 per tablet 250 mg tablet |
| Shortage now | No current entry | In shortage |
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