What the FDA labels say about taking them together
Isoniazid and propranolol
Propranolol's FDA label of January 15, 2026 names isoniazid in its drug interactions section; the isoniazid label PlainMeds reads does not name propranolol. The propranolol label: “… inhibitors of CYP1A2, such as imipramine, cimetidine, ciprofloxacin, fluvoxamine, isoniazid, ritonavir, theophylline, zileuton, zolmitriptan, and rizatriptan.”
Check it at the source: the isoniazid FDA label on DailyMed (effective July 8, 2025, OMNIVIUM PHARMACEUTICALS LLC.); the propranolol FDA label on DailyMed (effective January 15, 2026, Mylan Pharmaceuticals Inc.).
What does the isoniazid label say about propranolol?
Isoniazid's label (effective July 8, 2025) does not name propranolol in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (isoniazid), OMNIVIUM PHARMACEUTICALS LLC., effective July 8, 2025 (SPL set 35400f1d-fd25-4bfa-a382-ac390e21bf2e), via openFDA; the full label on DailyMed
What does the propranolol label say about isoniazid?
Propranolol label, drug interactionsSubstrates or Inhibitors of CYP1A2 Blood levels and/or toxicity of propranolol may be increased by co-administration with substrates or inhibitors of CYP1A2, such as imipramine, cimetidine, ciprofloxacin, fluvoxamine, isoniazid, ritonavir, theophylline, zileuton, zolmitriptan, and rizatriptan.
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
| Isoniazid | Propranolol | |
|---|---|---|
| Labeled for | n/a | High blood pressure, Angina, Atrial fibrillation, Migraine |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $3.40 per tablet 300 mg tablet | $0.0493 per tablet 20 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