What the FDA labels say about taking them together
Acetaminophen and isoniazid
Isoniazid's FDA label of July 8, 2025 names acetaminophen in its drug interactions section; the acetaminophen labels PlainMeds reads (4) do not name isoniazid. The isoniazid label: “Acetaminophen A report of severe acetaminophen toxicity was reported in a patient receiving isoniazid.”
Check it at the source: the acetaminophen FDA label on DailyMed (effective November 13, 2024, Kenvue Brands LLC); the isoniazid FDA label on DailyMed (effective July 8, 2025, OMNIVIUM PHARMACEUTICALS LLC.).
What does the acetaminophen label say about isoniazid?
Acetaminophen's label (effective November 13, 2024) and its 3 other brand-application labels do not name isoniazid in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Tylenol 8 HR Arthritis Pain), Kenvue Brands LLC, effective November 13, 2024 (SPL set 3af22fc8-e4e0-4863-8696-6bc1257047cb), via openFDA; the full label on DailyMed
What does the isoniazid label say about acetaminophen?
Isoniazid label, drug interactionsAcetaminophen A report of severe acetaminophen toxicity was reported in a patient receiving isoniazid.
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
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
| Acetaminophen | Isoniazid | |
|---|---|---|
| Labeled for | Fever, Cough and cold, Pain | n/a |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.0339 per unit 500 mg caplet | $3.40 per tablet 300 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