What the FDA labels say about taking them together
Diltiazem and propranolol
Diltiazem's FDA label of August 7, 2026 names propranolol in its drug interactions section, and propranolol's label names diltiazem too. The propranolol label: “The concomitant use of beta-adrenergic blockers and non-dihydropyridine calcium channel blockers, digoxin or clonidine increases the risk of significant bradycardia.”
Check it at the source: the diltiazem FDA label on DailyMed (effective August 7, 2026, Bausch Health US, LLC); the propranolol FDA label on DailyMed (effective January 15, 2026, Mylan Pharmaceuticals Inc.).
What does the diltiazem label say about propranolol?
Diltiazem label, drug interactionsAdministration of diltiazem hydrochloride concomitantly with propranolol in five normal volunteers resulted in increased propranolol levels in all subjects and bioavailability of propranolol was increased approximately 50%.
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
What does the propranolol label say about diltiazem?
Propranolol label, drug interactionsCo-administration of propranolol and diltiazem in patients with cardiac disease has been associated with bradycardia, hypotension, high-degree heart block, and heart failure.
Inderal Xl label (ANI Pharmaceuticals, Inc., August 27, 2026), warnings and precautionsThe concomitant use of beta-adrenergic blockers and non-dihydropyridine calcium channel blockers (e.g., verapamil and diltiazem), digoxin or clonidine increases the risk of significant bradycardia.
Source: FDA drug label (Inderal Xl, NDA021438), ANI Pharmaceuticals, Inc., effective August 27, 2026 (SPL set ac196ff5-9215-402b-bc57-69aa87f8bade), via openFDA
Source: FDA drug label (Propranolol Hydrochloride), Mylan Pharmaceuticals Inc., effective January 15, 2026 (SPL set b94dcec7-7633-4a33-9cea-48161adeaf93), 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
| Diltiazem | Propranolol | |
|---|---|---|
| Labeled for | High blood pressure, Angina, Atrial fibrillation | High blood pressure, Angina, Atrial fibrillation, Migraine |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.144 per capsule 24h ER(cd) 120 mg capsule | $0.0493 per tablet 20 mg tablet |
| Shortage now | A presentation being discontinued | 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