What the FDA labels say about taking them together
Cimetidine and diltiazem
Diltiazem's FDA label of August 7, 2026 names cimetidine in its drug interactions section; the cimetidine label PlainMeds reads does not name diltiazem. The diltiazem label: “A study in six healthy volunteers has shown a significant increase in peak diltiazem plasma levels (58%) and AUC (53%) after a 1-week course of cimetidine 1200 mg/day and a single dose of diltiazem 60 mg. …”
Check it at the source: the cimetidine FDA label on DailyMed (effective July 15, 2026, Mylan Pharmaceuticals Inc.); the diltiazem FDA label on DailyMed (effective August 7, 2026, Bausch Health US, LLC).
What does the cimetidine label say about diltiazem?
Cimetidine's label (effective July 15, 2026) does not name diltiazem in these sections. A label lists what its studies and reports found; it is not a complete list.
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 diltiazem label say about cimetidine?
Diltiazem label, drug interactionsA study in six healthy volunteers has shown a significant increase in peak diltiazem plasma levels (58%) and AUC (53%) after a 1-week course of cimetidine 1200 mg/day and a single dose of diltiazem 60 mg. Ranitidine produced smaller, nonsignificant increases.
Source: FDA drug label (Cardizem Cd, NDA020062), Bausch Health US LLC, effective December 10, 2025 (SPL set 1042fa13-e6af-46b9-8008-6c941f0978b1), via openFDA
Source: FDA drug label (Cardizem, NDA018602), Bausch Health US LLC, effective April 30, 2025 (SPL set f3e7ecef-f360-4987-a4f5-933214130ab2), via openFDA
Source: FDA drug label (TIAZAC EXTENDED RELEASE), Bausch Health US, LLC, effective August 7, 2026 (SPL set c567fe7e-887e-4291-a0d1-2dd3f25cbf25), 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 | Diltiazem | |
|---|---|---|
| Labeled for | Acid reflux and ulcers | High blood pressure, Angina, Atrial fibrillation |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.236 per tablet 300 mg tablet | $0.144 per capsule 24h ER(cd) 120 mg capsule |
| Shortage now | No current entry | A presentation being discontinued |
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