What the FDA labels say about taking them together
Methotrexate and sulfamethoxazole/trimethoprim
Methotrexate's FDA label (Rasuvo) of December 15, 2025 names sulfamethoxazole/trimethoprim in its drug interactions section, and sulfamethoxazole/trimethoprim's label names methotrexate too. The sulfamethoxazole/trimethoprim label: “Avoid concurrent use; Comments: Sulfonamides can also displace methotrexate from plasma protein binding sites and can compete with the renal transport of methotrexate, thus increasing free methotrexate concentrations.”
Check it at the source: the methotrexate FDA label on DailyMed (effective May 27, 2026, Accord Healthcare Inc.); the sulfamethoxazole/trimethoprim FDA label on DailyMed (effective December 30, 2024, Sun Pharmaceutical Industries, Inc).
What does the methotrexate label say about sulfamethoxazole/trimethoprim?
Rasuvo label (Medexus Pharma Inc., December 15, 2025), drug interactionsTrimethoprim/sulfamethoxazole has been reported rarely to increase bone marrow suppression in patients receiving methotrexate, probably by decreased tubular secretion and/or an additive antifolate effect.
Source: FDA drug label (Rasuvo, NDA205776), Medexus Pharma Inc., effective December 15, 2025 (SPL set d0075461-0e7e-4967-9c9b-d6440e912c0e), via openFDA
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 sulfamethoxazole/trimethoprim label say about methotrexate?
Sulfamethoxazole/trimethoprim label, drug interactionsDrug (s): Methotrexate; Recommendation: Avoid concurrent use; Comments: Sulfonamides can also displace methotrexate from plasma protein binding sites and can compete with the renal transport of methotrexate, thus increasing free methotrexate concentrations.
Source: FDA drug label (Sulfatrim, NDA018615), Preferred Pharmaceuticals, Inc., effective September 2, 2026 (SPL set cd4932ce-0856-4e99-8baf-70afce1d7ffd), via openFDA
Source: FDA drug label (Bactrim), Sun Pharmaceutical Industries, Inc, effective December 30, 2024 (SPL set f59d0c04-9c66-4d53-a0e1-cb55570deb62), 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 | Sulfamethoxazole/trimethoprim | |
|---|---|---|
| Labeled for | Rheumatoid arthritis, Psoriasis, Leukemia, lymphoma and myeloma, Breast cancer | Bacterial infections, Urinary tract infections, Diarrhea |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.158 per tablet 2.5 mg tablet | $0.0448 per tablet Sulfamethoxazole-tmp ds tablet |
| Shortage now | In shortage | 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