Methotrexate is a medication used to treat various conditions such as cancer, rheumatoid arthritis, and psoriasis. The efficacy of methotrexate can be influenced by several factors, including age.

According to Drug Patent Watch [1], methotrexate is approved by the FDA for use in adults and children with various conditions. However, the dosage and administration of methotrexate may vary depending on the patient's age, weight, and condition. The website does not provide specific information about how age affects methotrexate efficacy.

A study published in PubMed [2] investigated the effect of age on methotrexate efficacy in patients with rheumatoid arthritis. The study found that older patients (>65 years) required lower doses of methotrexate to achieve a therapeutic response compared to younger patients (<65 years). The study also found that older patients had a higher risk of methotrexate-related adverse effects. Therefore, the study suggests that age should be considered when determining the optimal dose of methotrexate for patients with rheumatoid arthritis.

A book chapter published in the National Library of Medicine [3] provides an overview of methotrexate use in older adults. The chapter notes that older adults may be more susceptible to methotrexate-related adverse effects due to age-related changes in pharmacokinetics and pharmacodynamics. The chapter also suggests that lower doses of methotrexate may be required in older adults to achieve therapeutic efficacy.

In summary, age can affect methotrexate efficacy in various ways. Older patients may require lower doses of methotrexate to achieve a therapeutic response, but they may also be more susceptible to methotrexate-related adverse effects. Therefore, age should be considered when determining the optimal dose of methotrexate for patients.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/METHOTREXATE
[2] https://pubmed.ncbi.nlm.nih.gov/1920331/
[3] https://www.ncbi.nlm.nih.gov/books/NBK556114/