What the FDA labels say about taking them together
Methotrexate and nitisinone
Nitisinone's FDA label of November 30, 2021 names methotrexate in its drug interactions section; the methotrexate labels PlainMeds reads (4) do not name nitisinone. The nitisinone label: “OAT1/OAT3 Substrates Clinical Impact Increased exposure of the interacting drug Intervention Monitor for potential adverse reactions related to the co-administered drug. …”
Check it at the source: the methotrexate FDA label on DailyMed (effective May 27, 2026, Accord Healthcare Inc.); the nitisinone FDA label on DailyMed (effective November 30, 2021, SWEDISH ORPHAN BIOVITRUM AB (PUBL)).
What does the methotrexate label say about nitisinone?
Methotrexate's label (effective May 27, 2026) and its 3 other brand-application labels do not name nitisinone 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 nitisinone label say about methotrexate?
Nitisinone label, drug interactionsOAT1/OAT3 Substrates (e.g., adefovir, ganciclovir, methotrexate) Clinical Impact Increased exposure of the interacting drug [see Clinical Pharmacology ( 12.3 )] Intervention Monitor for potential adverse reactions related to the co-administered drug. CYP2C9 Substrates: Increased systemic exposure of these co-administered drugs; reduce the dosage. Additional dosage adjustments may be needed to maintain therapeutic drug concentrations for narrow therapeutic index drugs. ( 7 ) OAT1/OAT3 Substrates: Increased systemic exposure of these co-administered drugs; monitor for potential adverse reactions.
Nityr label (Cycle Pharmaceuticals Ltd., December 22, 2025), drug interactionsOAT1/OAT3 Substrates (e.g., adefovir, ganciclovir, methotrexate) Clinical Impact Increased exposure of the interacting drug. [see Clinical Pharmacology ( 12.3 )] Prevention or Management Monitor for potential adverse reactions related to the co-administered drug.
Source: FDA drug label (Nityr, NDA209449), Cycle Pharmaceuticals Ltd., effective December 22, 2025 (SPL set 00fd1905-27e4-420e-8dc5-a69e4ddc1526), via openFDA
Source: FDA drug label (Orfadin), SWEDISH ORPHAN BIOVITRUM AB (PUBL), effective November 30, 2021 (SPL set 5d449b73-d503-4132-b978-d890491975df), 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 | Nitisinone | |
|---|---|---|
| Labeled for | Rheumatoid arthritis, Psoriasis, Leukemia, lymphoma and myeloma, Breast cancer | n/a |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.158 per tablet 2.5 mg tablet | n/a |
| 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