What the FDA labels say about taking them together
Methotrexate and piperacillin/tazobactam
Piperacillin/tazobactam's FDA label of July 21, 2025 names methotrexate in its drug interactions section; the methotrexate labels PlainMeds reads (4) do not name piperacillin/tazobactam. The piperacillin/tazobactam label: “Limited data suggests that co-administration of methotrexate and piperacillin may reduce the clearance of methotrexate due to competition for renal secretion.”
Check it at the source: the methotrexate FDA label on DailyMed (effective May 27, 2026, Accord Healthcare Inc.); the piperacillin/tazobactam FDA label on DailyMed (effective July 21, 2025, ONESOURCE SPECIALTY PHARMA LIMITED).
What does the methotrexate label say about piperacillin/tazobactam?
Methotrexate's label (effective May 27, 2026) and its 3 other brand-application labels do not name piperacillin/tazobactam in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Methotrexate), Accord Healthcare Inc., effective May 27, 2026 (SPL set 874c7f43-a3be-4236-89cc-24c44e3c5813), via openFDA; the full label on DailyMed
What does the piperacillin/tazobactam label say about methotrexate?
Piperacillin/tazobactam label, drug interactionsLimited data suggests that co-administration of methotrexate and piperacillin may reduce the clearance of methotrexate due to competition for renal secretion.
Source: FDA drug label (piperacillin and tazobactam), ONESOURCE SPECIALTY PHARMA LIMITED, effective July 21, 2025 (SPL set 28258745-12e4-4f0f-b318-4a1a1bebc928), 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
| Methotrexate | Piperacillin/tazobactam | |
|---|---|---|
| Labeled for | Rheumatoid arthritis, Psoriasis, Leukemia, lymphoma and myeloma, Breast cancer | Bacterial infections |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.158 per tablet 2.5 mg tablet | $3.49 per vial 3.375 g vial |
| Shortage now | In shortage | A presentation being discontinued |
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