What the FDA labels say about taking them together
Diphenhydramine and margetuximab
Margetuximab's FDA label of February 11, 2025 names diphenhydramine in its warnings and precautions section; the diphenhydramine label PlainMeds reads does not name margetuximab. The margetuximab label: “… intervene with medical therapy which may include epinephrine, corticosteroids, diphenhydramine, bronchodilators and oxygen.”
Check it at the source: the diphenhydramine FDA label on DailyMed (effective November 18, 2025, Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc.); the margetuximab FDA label on DailyMed (effective February 11, 2025).
What does the diphenhydramine label say about margetuximab?
Diphenhydramine's label (effective November 18, 2025) does not name margetuximab in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Diphenhydramine Hydrochloride), Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., effective November 18, 2025 (SPL set 6178d3a1-0741-49a4-be81-c4f7d29f8b2a), via openFDA; the full label on DailyMed
What does the margetuximab label say about diphenhydramine?
Margetuximab label, warnings and precautionsInterrupt MARGENZA infusion in patients experiencing dyspnea or clinically significant hypotension and intervene with medical therapy which may include epinephrine, corticosteroids, diphenhydramine, bronchodilators and oxygen.
Source: FDA drug label (MARGENZA), TerSera Therapeutics LLC, effective February 11, 2025 (SPL set 6a6d50c7-06ea-479c-83cc-f197a9e428c9), 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
| Diphenhydramine | Margetuximab | |
|---|---|---|
| Labeled for | Cough and cold, Allergies, Pain | Breast cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $0.898 per mL 50 mg/mL vial | n/a |
| 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