Understanding Folic Acid and Methotrexate: When It’s Helpful and When It’s Not

As healthcare providers, we often face the delicate decision of whether to pair folic acid with methotrexate, especially in patients with rheumatoid arthritis or psoriasis, where methotrexate is a key treatment.

Benefits of Folic Acid

Research consistently shows that adding folic acid (up to 50 mg per week) alongside low-dose methotrexate can reduce side effects without affecting its effectiveness. Folic acid helps counteract methotrexate-related increases in plasma homocysteine, improving patient outcomes and tolerability.

Important Considerations

However, caution is advised. A study with psoriasis patients found that folic acid could decrease methotrexate’s effectiveness in treating psoriasis. Similarly, a post-hoc analysis showed a 17% lower response rate in rheumatoid arthritis patients taking both methotrexate and folic acid compared to methotrexate alone.

Guidelines to Follow

1. For Non-Cancerous Conditions (like RA and psoriasis): Folic acid is recommended to reduce toxicity, but monitor carefully, as some patients may see reduced treatment effects.
2. For Cancerous Conditions: Avoid folic or folinic acid unless specifically directed, as it may lessen methotrexate’s effectiveness.

Final Thoughts

While folic acid can benefit many on methotrexate, its use should be personalized based on the specific condition. Engaging patients in discussions about benefits and risks can lead to better, more individualized treatment plans.