Drug interactions
Folic Acid + Methotrexate
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Overview
Folic acid can pharmacodynamically antagonize methotrexate’s antifolate effects, potentially reducing efficacy, particularly with high-dose oncologic regimens. In low-dose weekly methotrexate for rheumatologic/dermatologic disease, folic acid supplementation is recommended to reduce mucosal, GI, and hepatic toxicity and generally does not meaningfully impair clinical efficacy.
Mechanism of action
Pharmacodynamic antagonism: folate repletion bypasses dihydrofolate reductase inhibition and restores folate-dependent pathways; clinically mitigates toxicity with low-dose methotrexate but may lessen antineoplastic activity with high-dose therapy.
Clinical management
For low-dose weekly methotrexate (e.g., RA/psoriasis): co-prescribe folic acid 1 mg PO daily or 5 mg PO once weekly, typically 24–48 hours after the methotrexate dose; avoid administering on the same day as methotrexate in some protocols; monitor CBC and LFTs and assess disease control. For high-dose oncologic methotrexate: do not use folic acid outside protocol; follow leucovorin (folinic acid) rescue per oncology guidelines and avoid unplanned folate supplementation that could reduce antitumor efficacy.
Drug reference
References
- Folic acid and folinic acid for reducing side effects in patients receiving methotrexate for rheumatoid arthritis — Cochrane Database of Systematic Reviews
- Use of methotrexate in the treatment of rheumatoid arthritis — UpToDate
- Methotrexate Prescribing Information (US FDA Label) — FDA Label
- Methotrexate and Folic Acid – Drug Interactions — Lexicomp
Frequently asked questions
Can I take Folic Acid with Methotrexate?
The interaction is rated: Moderate. Folic acid can pharmacodynamically antagonize methotrexate’s antifolate effects, potentially reducing efficacy, particularly with high-dose oncologic regimens. In low-dose weekly methotrexate for rheumatologic/dermatologic disease, folic acid supplementation is recommended to reduce mucosal, GI, and hepatic toxicity and generally does not meaningfully impair clinical efficacy.
How serious is the interaction between Folic Acid and Methotrexate?
The interaction is rated: Moderate. Evidence level: High.
How is the interaction between Folic Acid and Methotrexate managed?
For low-dose weekly methotrexate (e.g., RA/psoriasis): co-prescribe folic acid 1 mg PO daily or 5 mg PO once weekly, typically 24–48 hours after the methotrexate dose; avoid administering on the same day as methotrexate in some protocols; monitor CBC and LFTs and assess disease control. For high-dose oncologic methotrexate: do not use folic acid outside protocol; follow leucovorin (folinic acid) rescue per oncology guidelines and avoid unplanned folate supplementation that could reduce antitumor efficacy.
Why do Folic Acid and Methotrexate interact?
Pharmacodynamic antagonism: folate repletion bypasses dihydrofolate reductase inhibition and restores folate-dependent pathways; clinically mitigates toxicity with low-dose methotrexate but may lessen antineoplastic activity with high-dose therapy.
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