What the FDA labels say about taking them together
Cyclophosphamide and trastuzumab
Cyclophosphamide's FDA label (Frindovyx) of August 26, 2026 names trastuzumab in its drug interactions section, and trastuzumab's label names cyclophosphamide too. The cyclophosphamide label: “Toxicity: Increased cardiotoxicity; Drugs: Anthracyclines Cytarabine Pentostatin Radiation therapy of the cardiac region Trastuzumab”
Check it at the source: the cyclophosphamide FDA label on DailyMed (effective January 19, 2026, Amneal Pharmaceuticals LLC); the trastuzumab FDA label on DailyMed (effective May 29, 2026, Genentech, Inc.).
What does the cyclophosphamide label say about trastuzumab?
Frindovyx label (AVYXA Pharma, LLC, August 26, 2026), drug interactionsACE inhibitors can cause leukopenia. ● Natalizumab ● Paclitaxel: Increased hematotoxicity has been reported when cyclophosphamide was administered after paclitaxel infusion. ● Thiazide diuretics ● Zidovudine Increased cardiotoxicity ● Anthracyclines ● Cytarabine ● Pentostatin ● Radiation therapy of the cardiac region ● Trastuzumab Increased pulmonary toxicity ● Amiodarone ● G-CSF, GM-CSF (granulocyte colony-stimulating factor, granulocyte macrophage colony-stimulating factor) Increased nephrotoxicity ● Amphotericin B ● Indomethacin:
Cyclophosphamide label (Eugia US LLC, April 21, 2025), drug interactionsToxicity: Increased cardiotoxicity; Drugs: Anthracyclines Cytarabine Pentostatin Radiation therapy of the cardiac region Trastuzumab
Source: FDA drug label (Frindovyx, NDA210852), AVYXA Pharma, LLC, effective August 26, 2026 (SPL set 5ad8ea65-4c98-487a-9c8d-df778765ec5e), via openFDA
Source: FDA drug label (Cyclophosphamide, NDA210735), Eugia US LLC, effective April 21, 2025 (SPL set 3c1eb470-0bba-457d-94e3-b9508f0d398a), via openFDA
Source: FDA drug label (Cyclophosphamide), Amneal Pharmaceuticals LLC, effective January 19, 2026 (SPL set 520bfe39-dfd5-4a20-9a37-80078afded0d), via openFDA; the full label on DailyMed
What does the trastuzumab label say about cyclophosphamide?
Trastuzumab label, warnings and precautionsNSABP B31 & NCCTG N9831 Median follow-up duration for NSABP B31 & NCCTG N9831 combined was 8.3 years in the AC→paclitaxel+Herceptin arm.; AC Anthracycline (doxorubicin) and cyclophosphamide. →Paclitaxel+Herceptin; 3.2% (64/2000) Includes 1 patient with fatal cardiomyopathy and 1 patient with sudden death without documented etiology.; 1.3% (21/1655)
Ogivri label (Mylan Institutional LLC, February 8, 2021), warnings and precautions1 & 2 Median follow-up duration for studies 1 and 2 combined was 8.3 years in the AC → TH arm.; AC Anthracycline (doxorubicin) and cyclophosphamide. → Paclitaxel + Trastuzumab; 3.2% (64/2000) Includes 1 patient with fatal cardiomyopathy and 1 patient with sudden death without documented etiology.; 1.3% (21/1655)
Source: FDA drug label (Kanjinti, BLA761073), Amgen, Inc, effective June 23, 2026 (SPL set 9a94f5b2-b84e-4987-8ea1-c4346db5a5fa), via openFDA
Source: FDA drug label (Herzuma, BLA761091), Cephalon, Inc., effective December 22, 2025 (SPL set ae71c003-883a-4cd8-ad50-e8cc9a54e971), via openFDA
Source: FDA drug label (Ogivri, BLA761074), Mylan Institutional LLC, effective February 8, 2021 (SPL set 6b7938e6-14c7-4a65-9605-967542ecfb8f), via openFDA
Source: FDA drug label (Herceptin), Genentech, Inc., effective May 29, 2026 (SPL set 492dbdb2-077e-4064-bff3-372d6af0a7a2), 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
| Cyclophosphamide | Trastuzumab | |
|---|---|---|
| Labeled for | Leukemia, lymphoma and myeloma | Breast cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.67 per capsule 50 mg capsule | 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