What the FDA labels say about taking them together
Cimetidine and warfarin
Cimetidine's FDA label of July 15, 2026 names warfarin in its drug interactions section, and warfarin's label names cimetidine too. The cimetidine label: “Clinically significant effects have been reported with the warfarin anticoagulants; therefore, close monitoring of prothrombin time is recommended, and adjustment of the anticoagulant dose may be necessary when …”
Check it at the source: the cimetidine FDA label on DailyMed (effective July 15, 2026, Mylan Pharmaceuticals Inc.); the warfarin FDA label on DailyMed (effective May 29, 2026, Amneal Pharmaceuticals LLC).
What does the cimetidine label say about warfarin?
Cimetidine label, drug interactionsClinically significant effects have been reported with the warfarin anticoagulants; therefore, close monitoring of prothrombin time is recommended, and adjustment of the anticoagulant dose may be necessary when cimetidine tablets are administered concomitantly.
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 warfarin label say about cimetidine?
Warfarin label, drug interactionsClosely monitor INR if a concomitant drug is a CYP2C9, 1A2, and/or 3A4 inhibitor or inducer. Examples of CYP450 Interactions with Warfarin Enzyme Inhibitors Inducers CYP2C9 amiodarone, capecitabine, cotrimoxazole, etravirine, fluconazole, fluvastatin, fluvoxamine, metronidazole, miconazole, oxandrolone, sulfinpyrazone, tigecycline, voriconazole, zafirlukast aprepitant, bosentan, carbamazepine, phenobarbital, rifampin CYP1A2 acyclovir, allopurinol, caffeine, cimetidine, ciprofloxacin, disulfiram, enoxacin, famotidine, fluvoxamine, methoxsalen, mexiletine, norfloxacin, oral contraceptives, phenylpropanolamine, propafenone, propranolol, terbinafine, thiabendazole, ticlopidine, verapamil …
Source: FDA drug label (Warfarin Sodium), Amneal Pharmaceuticals LLC, effective May 29, 2026 (SPL set 558b7a0d-5490-4c1b-802e-3ab3f1efe760), 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 | Warfarin | |
|---|---|---|
| Labeled for | Acid reflux and ulcers | Blood clots (DVT and PE), Atrial fibrillation |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.236 per tablet 300 mg tablet | $0.093 per tablet 2 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