<p>Methotrexate is a folate derivative that inhibits several enzymes responsible for nucleotide synthesis.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Inoue K, Yuasa H: Molecular basis for pharmacokinetics and pharmacodynamics of methotrexate in rheumatoid arthritis therapy. Drug Metab Pharmacokinet. 2014;29(1):12-9. Epub 2013 Nov 26. (PubMed ID 24284432)" href="#reference-A180322">1</a></sup> This inhibition leads to suppression of inflammation as well as prevention of cell division.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Inoue K, Yuasa H: Molecular basis for pharmacokinetics and pharmacodynamics of methotrexate in rheumatoid arthritis therapy. Drug Metab Pharmacokinet. 2014;29(1):12-9. Epub 2013 Nov 26. (PubMed ID 24284432)" href="#reference-A180322">1</a></sup> Because of these effects, methotrexate is often used to treat inflammation caused by arthritis or to control cell division in neoplastic diseases such as breast cancer and non-Hodgkin's lymphoma.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Inoue K, Yuasa H: Molecular basis for pharmacokinetics and pharmacodynamics of methotrexate in rheumatoid arthritis therapy. Drug Metab Pharmacokinet. 2014;29(1):12-9. Epub 2013 Nov 26. (PubMed ID 24284432)" href="#reference-A180322">1</a>,<a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Oral Solution" href="#reference-L7144">4</a>,<a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Subcutaneous Injection" href="#reference-L7147">5</a>,<a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Prefilled Syringe for Subcutaneous Injection" href="#reference-L7150">6</a>,<a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Injection" href="#reference-L7180">7</a></sup></p><p>Due to the toxic effects of methotrexate, it is indicated for treatment of some forms of arthritis and severe psoriasis only if first line treatment has failed or patients are intolerant of those treatments.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Injection" href="#reference-L7180">7</a></sup></p><p>Methotrexate was granted FDA approval on 7 December 1953.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Sodium Oral Tablets" href="#reference-L7198">8</a></sup></p>