What the FDA labels say about taking them together
Allopurinol and cyclophosphamide
Allopurinol's FDA label of May 21, 2026 names cyclophosphamide in its drug interactions section; the cyclophosphamide labels PlainMeds reads (4) do not name allopurinol. The allopurinol label: “Clinical Impact; Concomitant use of allopurinol with cyclophosphamide and other cytotoxic agents increases bone marrow suppression among patients with neoplastic disease, except leukemia.”
Check it at the source: the allopurinol FDA label on DailyMed (effective May 21, 2026, Rising Pharma Holdings, Inc.); the cyclophosphamide FDA label on DailyMed (effective January 19, 2026, Amneal Pharmaceuticals LLC).
What does the allopurinol label say about cyclophosphamide?
Allopurinol label, drug interactionsClinical Impact; Concomitant use of allopurinol with cyclophosphamide and other cytotoxic agents (doxorubicin, bleomycin, procarbazine, mechloroethamine) increases bone marrow suppression among patients with neoplastic disease, except leukemia.
Allopurinol label (Proficient Rx LP, February 1, 2023), drug interactionsEnhanced bone marrow suppression by cyclophosphamide and other cytotoxic agents has been reported among patients with neoplastic disease, except leukemia, in the presence of allopurinol.
Source: FDA drug label (Allopurinol, NDA018877), Proficient Rx LP, effective February 1, 2023 (SPL set 0ca4baed-c5d8-4de4-ac17-6e5d1df15c03), via openFDA
Source: FDA drug label (Allopurinol), Rising Pharma Holdings, Inc., effective May 21, 2026 (SPL set 30ad5ba2-1cef-4933-b104-0597f6a2aaa2), via openFDA; the full label on DailyMed
What does the cyclophosphamide label say about allopurinol?
Cyclophosphamide's label (effective January 19, 2026) and its 3 other brand-application labels do not name allopurinol in these sections. A label lists what its studies and reports found; it is not a complete list.
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
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
| Allopurinol | Cyclophosphamide | |
|---|---|---|
| Labeled for | Gout | Leukemia, lymphoma and myeloma |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $0.0315 per tablet 100 mg tablet | $1.67 per capsule 50 mg capsule |
| Shortage now | A presentation being discontinued | 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